US 4906907

I'll search for the specific patent number and any 2026 CAFC docket activity.

Let me run a couple more targeted checks for any 2026 litigation/appeal activity and status.

Summary of US Patent 4,906,907

Search scope note: I queried for the specific number 4906907 (and 4,906,907) against patent databases and CAFC 2026 Federal Circuit material. I found no CAFC 2026 docket, appeal, IPR, or litigation activity involving US 4,906,907. This is unsurprising given the patent's status (below). One caution: searching the bare string 4906907 also surfaces JP4906907B2 ("Device and method for filling a foil bag with food," expired – fee related) — that is a different, unrelated document (a Japanese publication number), not US 4,906,907. I did not conflate them.

Bibliographic data (from the authoritative full text and corroborating sources)

Sources: https://patents.google.com/patent/US4906907/en ; https://uspto.report/patent/grant/4906907 ; https://www.freepatentsonline.com/4906907.html

Abstract (verbatim)

"A robot system in which a force (torque) exerted on an end effector disposed at an end of a robot to hold an object is sensed to achieve a positioning control. The robot system includes a unit to sense an inertial force exerted on the end effector and the sensed result is fed back so as to remove the influence of the inertia force, thereby effecting an accurate positioning control."

Technical problem and core idea

The patent starts from the conventional "virtual compliance" force-control approach (citing Sugimoto et al., US 4,621,332, also Hitachi; and the 1986 Digests of the Society of Instrument and Control Engineers paper, Vol. 22, No. 3, pp. 343–349). In that approach, the raw sensor value Q is treated as the pure external force q. The patent observes that Q actually includes an inertia term [m]·(dv/dt) (Eq. 2), where [m] is the combined mass of gripper and payload. Negligible for small masses on Earth, this term becomes dominant for large payloads and in microgravity (space) operations. The claimed fix: directly sense the inertia force (via accelerometers, vision, or joint-position differentiation) and subtract it from the force-sensor reading to obtain the true external force used for control.

Plain-language overview of each independent claim

• Claim 1 (base apparatus claim). A robot with at least one joint, a joint driver, and a gripper/holder at the end with its own actuator. Two sensing subsystems: (a) one sensing force/torque on the holder, and (b) one sensing the inertia force exerted on the holder. A control unit takes both sensed results, computes a corrected external force by subtracting the sensed inertia force (including that of the grasped object) from the sensed force, and drives the joints according to that corrected value. Note: the claim opens by introducing the force sensor only as "sense means" but later refers to "said first sense means," an antecedent-basis irregularity in the granted text; also "by subtraction a sensed inertia force" is the literal wording — I reproduce it verbatim rather than correcting it.

• Claim 7 (three-sensor apparatus claim). Same as claim 1, but adds a third sensing means for sensing an inertia force exerted on the robot itself (i.e., the manipulator/arm, e.g. an accelerometer at the base or on the arm — described as located between the base and the root of the robot), with the joints controlled in dependence on all three sensed results. Note: the claim text says "sense means for sensing an inertia force effected on said hold means" — this is presumably meant as the "second" sense means but is not numbered as such in the granted wording.

• Claim 14 (control-path / signal-correction claim). A robot with joint drive devices and a gripper. A first sensor senses force/torque on the holder, and a controller generates joint-drive commands from that sensor's output. Separately, a second sensor senses inertia force on the holder, and a correction stage modifies the controller's output signals before they reach the joint drives, so that the object's inertia force is removed from the sensed force.

• Claim 19 (microgravity base claim). Essentially claim 1 recast as "a robot system in a microgravity condition," using "gripper means" and "actuation means" terminology, with the same subtraction-based corrected-external-force control.

• Claim 20 (microgravity three-sensor claim). Essentially claim 7 recast in microgravity terms: force/torque sensor on the gripper, second sensor for gripper inertia force, third sensor for the robot's own inertia force, control based on all three.

• Claim 22 (microgravity control-path claim). Essentially claim 14 recast for microgravity: controller generates joint-drive signals from the gripper force/torque sensor, and a correction stage alters those signals based on the gripper inertia-force sensor before supplying them to the joint drives.

Dependent claims (grouped)

• Sensor type for the "inertia" sensing means — an acceleration sensor (claims 2, 8, 15).
• Vision-based alternative — image detection means plus an image processor analyzing the captured image (claims 3, 9, 16).
• Joint-position alternative — position detectors at the joints plus an arithmetic unit processing their signals (claims 4, 10, 17).
• Integrated sensor unit — force/torque sensor and inertia sensor combined in one unit mounted between the robot end and the holder (claims 5, 11, 18; and 21 for the microgravity variant).
• Control details — generating drive target values from the first sensor and correcting them using the second sensor (claims 6, 13).
• Location of the third (robot-inertia) sensor — connected between the base securing the robot and the root portion of the robot (claims 12 and 21).

Disclosed embodiments (for context)

1. Accelerometers at the end effector and at the base (FIGS. 1–5), with the force sensor and accelerator optionally integrated in one unit (FIG. 5).
2. Vision system + vision processor; if the image is stationary the inertia force is assumed zero, if moving the processor computes image velocity/acceleration to remove the inertia component (FIG. 6).
3. Joint position detectors (601–606) feeding a sub-controller that differentiates position twice in time to get acceleration (FIG. 7).
4. Direct servo-gain modulation by a sub-controller feeding gain commands to the power/servo amplifier without going through the central CPU — increase gain for all axes when position signals are changing, decrease gain on the loaded axis when position signals are static (FIG. 8).
5. The patent also discloses on-line estimation of unknown mass/inertia M1 by slightly moving the manipulator immediately after grasping an object with no external force, then solving m = F'/a' and I' = M'/α', averaging over several sample points.

Uncertainty / caveats

• No CAFC 2026 activity found. I could not locate any Federal Circuit docket, appeal, or litigation referencing US 4,906,907. I do not have direct authenticated access to PACER/CM-ECF or the CAFC's docket system from these searches, so I state this as "no evidence found," not as a certainty that none exists.
• Legal status is shown by Google Patents as "Expired – Lifetime," which Google itself labels as an assumption, not a legal conclusion. Since the 20-year term from the 1988-03-30 filing would have run to 2008-03-30, and the last recorded maintenance payment was the 12-year fee in 2001, an assertion of this patent in 2026 is not plausible.
• Claim-text irregularities (e.g., "by subtraction a sensed inertia force," "effected on," and the missing explicit "first/second" numbering in claims 1 and 7) appear in the granted text as reproduced by Google Patents and FreePatentsOnline; I have quoted them literally rather than normalizing them. I have not independently verified the official USPTO printed copy of the claims line-by-line.
• The JP 2713899B2 family member and the unrelated JP4906907B2 are distinct documents; do not treat them as the same patent.

I'll search for litigation involving US patent 4906907 across patent litigation sources.

Let me search dedicated litigation databases and patent-specific sources.

Litigation Report — U.S. Patent No. 4,906,907

Patent: U.S. 4,906,907 ("Robot system")
Inventors: Akira Tsuchihashi; Shinichi Takarada
Assignee: Hitachi, Ltd.
App. No. 07/175,318 · Filed 1988‑03‑30 · Priority 1987‑03‑30 (JP 62‑74001) · Granted 1990‑03‑06
Status (per Google Patents): Expired – Lifetime; anticipated expiration 2008‑03‑30 (i.e., full 20‑year term from filing).

Finding

No litigation involving U.S. Patent No. 4,906,907 was identified.

My searches of patent‑litigation resources (Google Patents litigation data, Unified Patents portal references, CourtListener/RECAP, Docket Alarm, uspto.report, and general web) returned no district court, ITC, PTAB, or CAFC proceeding in which U.S. 4,906,907 was asserted, challenged, or adjudicated.

Because no case was found, I cannot provide the plaintiff/defendant/jurisdiction/case‑number/filing‑date/outcome fields you requested — there is no case to populate them with.

Important disambiguation (per your "interpret literally / do not auto‑correct" rule)

My searches surfaced several near‑match identifiers that are NOT U.S. 4,906,907. I am flagging these explicitly so they are not mistaken for litigation on this patent:

None of these are a lawsuit involving U.S. 4,906,907.

Reasoning / supporting evidence

• Google Patents record for US4906907A lists no "Litigation" entries — only classification, family, citations, and citing documents. Patents that have been litigated generally display a litigation section there. (https://patents.google.com/patent/US4906907A)
• The patent is recorded as "Expired – Lifetime" with an anticipated expiration of 2008‑03‑30 and no post‑grant adversarial proceedings (no IPR/PGR/reissue noted in the legal events; only routine maintenance‑fee payments through the 12‑year fee). (Google Patents "Legal Events")
• uspto.report entry for grant 4906907 shows only prosecution/assignment data (Hitachi, Ltd.; inventors Tsuchihashi and Takarada) and no associated litigation. (https://uspto.report/patent/grant/4906907)
• Unified Patents and Docket Alarm/PTAB search results discussed other patents (e.g., 7,177,690; 9,606,907; 10,013,158; 10,311,073) and never this patent.

Caveats / limits of this finding

• I do not have direct, real‑time access to PACER or a commercial docket database (LEXIS/Westlaw/Docket Navigator); this finding rests on publicly indexed sources plus the patent's own record. A PACER/Docket Navigator check could catch a minor, short‑lived, or sealed 1988–2008 filing that is not web‑indexed.
• Given the patent's age (granted 1990, expired 2008) and its subject matter (space/microgravity robot force‑torque control), any enforcement would most likely have occurred — if at all — in the 1990s, and would typically involve Hitachi, Ltd. as plaintiff.
• I do not know of any such case with high confidence beyond the negative search result above; I am stating this explicitly rather than inferring.

Bottom line: Based on the sources searched, there is no known litigation involving U.S. Patent No. 4,906,907. If you need a definitive negative, I recommend a PACER/Docket Navigator query on the patent number and on "Hitachi" for the 1990–2008 period.

I'll verify the structured data with targeted searches before finalizing.

Let me run a couple more confirmatory searches, including for reexamination history.

One more check for litigation/appeal dockets to round out the defensive picture.

Proceedings overview

Zero AIA trial proceedings on file — 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The USPTO Open Data Portal returns no IPR, PGR, or CBM for US 4,906,907, and my web searches surfaced no PTAB or Federal Circuit activity tied to this patent number. The bottom-line defensive posture is not "the patent has survived and is hardened" — it is far stronger than that: US 4,906,907 expired on 2008-03-30, roughly four and a half years before the first IPR was ever filed (2012-09-16), so no AIA trial was even procedurally available while the patent was enforceable. All 22 claims stand as issued, but every one of them lapsed more than 17 years ago. Any demand letter citing this patent today is asserting a dead patent.

No proceeding to docket

There is no IPR20XX-XXXXX, PGR20XX-XXXXX, or CBM20XX-XXXXX to populate the per-proceeding template. I will not fabricate a proceeding number to fill the format. The applicable facts supporting the null result are:

Why the null result is structural, not accidental:

• IPR (35 U.S.C. §§ 311–319) became available 2012-09-16 — after this patent's 2008-03-30 expiry. There was no enforceable term left to attack.
• PGR is limited to patents having a claim with an effective filing date on or after 2013-03-16. This patent's effective filing date is 1987-03-30. Statutorily ineligible.
• CBM is limited to patents covering a "financial product or service" (AIA § 18(d)). A force/torque-sensing robot positioning control is not a covered business method patent.

Verification caveat (stated plainly): I do not have a live authenticated query into PTAB E2E / PTAB Center, and the searches I ran returned patent-content pages (Google Patents, FPO, uspto.report, searchlight.law, RPX Insight) rather than any Board filing. I therefore can confirm the ODP "no proceedings" result and the absence of surfaced PTAB/CAFC activity, but I cannot give you a certified E2E docket screenshot. Given the 2008 expiry, an undiscovered AIA trial is close to impossible; a petition filed years after expiration on a dead patent would have no economic purpose.

False-positive warning — do not confuse this patent with the "907 patent" in litigation

Search results for "907 patent" litigation (e.g., the Netlist v. SK hynix, ITC Inv. No. 337-TA-1089 materials, and IPR2024-00714) refer to U.S. Patent No. 7,916,907 (memory device "receive/do-not-receive" claims) and U.S. Patent No. 10,627,907 (haptic user-input element), respectively. Neither has any relationship to Tsuchihashi/Takarada's US 4,906,907. If someone hands you an "SK hynix invalidated the '907 patent" narrative, it is not about this patent.

Strategic summary

Claim status: all 22 claims stand as issued — but all are expired. No claim of US 4,906,907 has ever been canceled, narrowed by reissue/reexam, or held unpatentable, because no adversarial validity proceeding was ever brought (or bringable) against it. So the "surviving claims" are claims 1–22 in their original form, and the "canceled claims" set is empty. The relevant status is not validity, it is enforceability over time: the patent's 20-year term from the 1988-03-30 filing expired 2008-03-30, and the maintenance fees were paid through the 12-year window (last recorded fee payment 2001-08-30, "Year of fee payment: 12"), consistent with a full-term expiry rather than an early lapse for non-payment.

Estoppel: not applicable, and that is the point. § 315(e)(2) estoppel only attaches to a petitioner who lost a final written decision or whose petition was instituted and later terminated. With no petitioner and no institution, there is no estoppel on anyone — and equally, no IPR-based defense to inherit. If you were building a defense, you would not need § 102/§ 103 at all: the affirmative defense is expiration plus the statute of limitations. Under 35 U.S.C. § 286, damages reach back only six years from complaint; the patent's last six-year recovery window closed in 2014-03-30. There is no hypothetical royalty base today because there is no exclusive right today.

Pattern signals: a single, cold, corporate-owned patent. No serial petitioner behavior (no petitioner at all). No PTAB-appeal pattern. No defensive aggregator — no Unified Patents, RPX, or Open Invention Network IPR appears in the record for this number; the RPX Insight page that surfaces in search is merely a patent-profile entry, not a proceeding. The family is a 1980s Hitachi space-robotics portfolio item (see the spacecraft embodiment in FIG. 3 and the microgravity claims 19–22), developed under Japan's space-manipulator research of that era; its citations include Hitachi's own U.S. Pat. No. 4,621,332 to Sugimoto and contemporaneous Unimation/MIT manipulator-compliant-motion art.

Where the prior art risk would sit, if the patent were alive. The 13 examiner-cited references — notably US 4,621,332 (Hitachi) and US 4,603,284 / US 4,279,920 (Unimation, resolved compliant motion) — plus the non-patent literature ("Virtual Compliance Control of Multiple Degree of Freedom Robot," SICE Vol. 22, No. 3, Mar. 1986, pp. 343–349; Paul, Robot Manipulators) would be the § 103 attack surface for the inertia-compensation limitation of claims 1, 19, and 22. Note that the 1983-09-02 Hitachi Japanese application JPS6052296A, "Method of correcting force sensor output," appears in the family-citation history — a force-sensor-output-correction reference that a hypothetical petitioner would likely pair against the claimed "subtracting inertial force from sensed force." This is academic now, but it tells you the patent was never a strong candidate for survival had it been tested.

Recommended next steps

• You are not a defendant; you cannot be one. Do not spend budget on invalidity, IPR strategy, or estoppel analysis for this patent. US 4,906,907 expired 2008-03-30 (Google Patents legal status: "Expired – Lifetime"). ["Infringement" of an expired patent is legally impossible after expiration, and pre-expiration damages are time-barred under § 286.]
• If you received a demand letter citing US 4,906,907: treat it as a strong indicator of a non-practicing-entity shakedown or an incompetent/erroneous demand. Demand the patent's expiration date, the accused product with a date-of-sale before 2008-03-30, and the compliant date. A properly grounded response is a one-paragraph § 286/expiration letter, not a claim-construction fight. Also verify the sender actually has standing — the patent was assigned to Hitachi, Ltd. at grant (Reel/Frame 004857/0032, effective 1988-03-16), and any present "owner" must show an unbroken chain.
• There is no FWD to link, no E2E docket to monitor, and no trial-stage milestone to calendar. Because there is no proceeding, there is no institution deadline, no oral hearing, and no statutory one-year FWD clock running. Nothing here needs a docket watch.
• The absence of PTAB activity is itself the signal. Well-asserted, live patents eventually attract IPRs. A 1990 robot-control patent that expired in 2008 and drew zero IPRs, zero CBMs, and zero Federal Circuit appeals was never commercially asserted during its enforceable life — which is exactly what you would expect for a niche space-robotics implementation patent.

Sources used: USPTO ODP structured "PTAB proceedings on file" block (no proceedings); Google Patents, https://patents.google.com/patent/US4906907/en (claims, expiration, family, citation lists); FreePatentsOnline, https://www.freepatentsonline.com/[4906907](/patent/4906907).html; RPX Insight, https://insight.rpxcorp.com/patent/[US4906907A](/patent/US4906907A). Searches for PTAB/CAFC activity on this patent number returned no Board or appellate filings; the "907 patent" hits in ITC Inv. No. 337-TA-1089 and IPR2024-00714 concern different patents (US 7,916,907 and US 10,627,907) and are flagged above as name collisions.

I'll reconstruct the assignment record for US 4906907. Let me pull the available records.

Assignment Record Reconstruction — US 4,906,907 ("Robot system")

Data-source note: The USPTO Patent Assignment Search (assignmentcenter.uspto.gov / assignment.uspto.gov) is a JavaScript application and its per-record views were not directly retrievable through the search tooling available for this report. The assignment data below is taken from the authoritative Google Patents Legal Events table for US4906907A (which mirrors the USPTO Assignment Center records, including reel/frame), cross-checked against uspto.report and the patent family data. Where the Assignment Center would ordinarily show a correspondent of record for the recording, that field is not disclosed in the indexed record for this patent; I flag that explicitly rather than guess.

Inventors

Both inventors are attributed to Hitachi (Akira Tsuchihashi is credited with 11 Hitachi-assigned patents per PatentLeaderboard). The application carries a Japanese priority claim to JP 62-74001, filed 1987-03-30 — i.e., this is an outbound filing from Hitachi's Japanese R&D, and both inventors assigned their rights to Hitachi by the standard employee-invention instrument.

Unusual patterns: None. There is no evidence that either inventor departed Hitachi within 12 months of filing, no co-inventor scattered across unrelated assignees, and the two inventors signed the assignment to the same corporate employer. No fire-sale precursor.

Original assignee

Hitachi, Ltd. (a corporation of Japan), 6, Kanda Surugadai 4-chome, Chiyoda-ku, Tokyo — as recorded on assignment reel 004857/0032 and confirmed by uspto.report ("currently assigned to Hitachi, Ltd.").

• Primary line of business: Diversified industrial/electrical conglomerate (heavy industry, electronics, information systems, and an established industrial-robotics product line). The claims cover a force/torque-sensed robot control loop compensated for end-effector inertia — squarely within Hitachi's robotics controls R&D of the mid-1980s.
• Did they ship a product embodying the claims? Not determinable from the record with high confidence. The specification frames the application around microgravity/spacecraft manipulation (FIG. 3 depicts a spacecraft-mounted manipulator), which suggests at least a partly research/feasibility orientation, although the claims themselves are generic force-controlled robots. I do not have evidence of a specific commercial Hitachi robot model reading on claim 1, so I will not assert one.
• Current status: Operating. Hitachi, Ltd. remains a going concern, publicly listed in Tokyo (TYO: 6501). No bankruptcy, no dissolution, no NPE acquisition. Hitachi itself has never been a patent-assertion plaintiff on this patent (see below).

Assignment timeline

Chronological list of every recorded assignment found:

• 1988-03-16 (executed) / recorded 1988-03-30 — Reel 004857/0032
  • Conveyance: Assignment — "ASSIGNMENT OF ASSIGNORS INTEREST"
  • Assignor: TSUCHIHASHI, AKIRA and TAKARADA, SHINICHI (individually)
  • Assignee: HITACHI, LTD., A CORP. OF JAPAN, 6 Kanda Surugadai 4-chome, Chiyoda-ku, Tokyo
  • Correspondent: Not disclosed in the indexed record. The only address captured is the assignee's own Chiyoda-ku, Tokyo address, not a recording attorney or service-of-process agent. This is consistent with the routine in-house/Japanese-counsel handling of an inventor-to-employer assignment at filing, but it cannot be confirmed from the available data.
  • Context: Standard employee-invention assignment at filing — inventors assign to their employer as a condition of the original corporate filing. Not an acquisition, not a fire-sale, not a reorg.

No post-issuance assignments are recorded. The patent's remaining legal events are administrative only:

This is itself the finding: the ownership chain is exactly one link long, terminates at the original operating-company assignee, and was never assigned, licensed-by-record, collateralized, or transferred after grant. There is no NPE chain to reconstruct.

Timeline diagram

timeline
    title Ownership of US 4906907
    1987 : Priority application filed in Japan
    1988 : US application filed 30 March
         : Assignment recorded to Hitachi Ltd
         : Reel 004857 frame 0032
    1990 : US patent issued 6 March
    1993 : Maintenance fee year 4 paid
    2008 : Patent reached expiry

NPE / troll-pattern signals

1. Shell-entity transfer — not present. No assignment out of Hitachi, Ltd. to any LLC, IP-holding vehicle, or licensing entity appears on reel 004857/0032 or anywhere else in the record. The sole recorded assignee is an operating Japanese conglomerate at its own corporate address.

2. Known asserter in the chain — not present. Hitachi, Ltd. appears on no RPX / Unified Patents high-frequency-plaintiff list. No Acacia, Marathon, Intellectual Ventures, Wi-LAN/Conversant, Mosaid, Vringo, Pendrell, Round Rock, or Spangenberg-affiliated entity appears as assignee anywhere in the chain or in the family (JP2713899B2, CA1330363C, DE3810691A1/C2) — all remain with Hitachi-side ownership.

3. Repeat correspondent across the chain — not assessable. There is only one recorded assignment, so the "same lawyer on multiple links" signal cannot exist by definition. Because the correspondent field is not disclosed in the indexed record, I cannot name an attorney or firm — and I will not infer one from the assignee's Tokyo address.

4. Cascading transfers — not present. One assignment total, executed 1988-03-16, with no subsequent assignment in 38 years of recorded history.

5. Pre-litigation transfer — not present. No assignment within 6 months before any infringement suit — because no lawsuit naming US 4,906,907 has been found. The patent expired 2008-03-30 without ever being asserted.

6. Bankruptcy fire-sale — not present. Hitachi, Ltd. has not filed Chapter 7 or Chapter 11. No patent-sale vehicle (Kodak/Nortel/Polaroid-style) is implicated.

7. Privateering — not present. No operating-company-to-NPE transfer exists here, so there is no privateer arrangement. Notably, later Hitachi continuation work on the same subject matter (e.g., US5130632, US5378968, both Hitachi-assigned and citing this patent's family) stayed in-house, which is affirmative evidence Hitachi retained and continued to prosecute the portfolio rather than spinning it out.

8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at expiry in the hands of the original owner.

Verdict

Insufficient data — in the specific sense intended here: the Assignment Center record for US 4,906,907 contains only the original assignment (Hitachi inventors → Hitachi, Ltd., reel 004857/0032, executed 1988-03-16, recorded 1988-03-30). There is no post-issuance assignment, no licensing record, and no assertion activity. Every NPE-pattern signal is not present, and the controlling data point is that the patent expired on 2008-03-30 with Hitachi, Ltd. still the owner of record after paying maintenance fees through year 12 (last fee 2001-08-30). This patent is a clean single-assignee, operating-company portfolio asset, not an NPE vehicle.

Verify at: USPTO Patent Assignment Search — https://assignment.uspto.gov/patent/index.html#/patent/search?q=4906907 (search 4906907; the single hit should be reel 004857/0032, Hitachi, Ltd.). Companion record: https://uspto.report/patent/grant/4906907 ("currently assigned to Hitachi, Ltd.").

Caveats: (a) The USPTO Assignment Center UI itself could not be queried directly for this report, so the reel/frame and dates are sourced from the Google Patents Legal Events mirror and uspto.report rather than a live Assignment Center screenshot; a manual lookup should be run to confirm no record was omitted. (b) The correspondent of record for reel 004857/0032 is not exposed in the indexed data; I have not named one, because doing so from the Tokyo assignee address alone would be fabrication.

I'll verify the patent record and research each cited prior-art reference.

Prior-Art Analysis — U.S. Patent No. 4,906,907

Patent under analysis: U.S. 4,906,907 — "Robot system"
Inventors: Akira Tsuchihashi; Shinichi Takarada · Assignee: Hitachi, Ltd.
App. No. 07/175,318 · Filed 1988‑03‑30 · JP priority 1987‑03‑30 (JP 62‑74001)
Granted 1990‑03‑06 · Status: Expired – Lifetime (anticipated expiration 2008‑03‑30)
Sources consulted: the authoritative full text supplied in this task (Google Patents, https://patents.google.com/patent/[US4906907](/patent/US4906907)/en), the FPO record (https://www.freepatentsonline.com/4906907.html), uspto.report (https://uspto.report/patent/grant/4906907). Because this patent was filed in 1988, pre‑AIA 35 U.S.C. § 102(a)–(g) governs. The § 102(b) statutory-bar critical date is 1987‑03‑30 (one year before the U.S. filing date; the JP priority cannot antedate a § 102(b) reference).

Note on scope discipline: I did not find any reference with "4906907" in its own number — all results for that string resolve to this very patent or to unrelated coincidental matches (e.g., a Japanese "4906907 B2" foil-bag patent). The references below are the ones the patent itself lists as cited prior art.

1. The invention in one line (for claim-mapping)

Every independent claim (1, 7, 14, 19, 20, 22) requires two senses plus a subtraction: (i) a force/torque sensor on the end effector ("hold means"/"gripper means"), (ii) a second means for sensing the inertia force exerted on that end effector, and (iii) control means that subtract the sensed inertia force from the sensed force to obtain a corrected external force that drives the robot. Claims 7/20 add a third inertia sense (on the robot/base); dependent claims specify an acceleration sensor (2, 8, 15), a vision/image system (3, 9, 16), joint position detectors + arithmetic unit (4, 10, 17), an integrated sensor unit (5, 11, 18, 21), and target-value generation/correction (6, 13).

This "sense-and-subtract the inertia force" feature is the point of novelty, and it is what every cited reference lacks. That drives the § 102 result below.

2. U.S. patent references cited (13) — the "look at each citation" set

3. Foreign / family references appearing on the record

These appear in the "Family Cites Families" set (i.e., cited against the JP/DE/CA counterparts, not necessarily against the U.S. case). Two are substantively closer than most U.S. cites and are flagged accordingly:

• JP S60‑52296 A — "Method of correcting force sensor output," Hitachi, publ. 1985‑03‑25 (§ 102(b)). Directly about correcting a force-sensor output — the closest topical foreign reference to the patent's correction concept, though the available record does not show it teaching an inertia-force term.
• JP S60‑77210 A — "Controlling method of spatial kinetic mechanism," NTT, publ. 1985‑05‑01 (§ 102(b)). Spatial-dynamics control; relevant background to the inertia term.
• JP S58‑206394 A — "Robot position correction method," Hitachi, publ. 1983‑12‑01 (§ 102(b)). Position-correction background.
• JP S61‑217802 A — "Robot controller," Omron Tateisi Electronics, publ. 1986‑09‑27 (§ 102(b)). General robot controller.
• DE 30 39 400 C2 — Method for controlling handling systems, Pietzsch, publ. 1984‑10‑04 (§ 102(b)). Handling-system control.
• DE 32 44 211 A1 — Orbital remote-controlled manipulator system, ERNO Raumfahrttechnik, publ. 1984‑05‑30 (§ 102(b)). Relevant to the space/microgravity context of claims 19–22, but does not teach the force-minus-inertia-force subtraction.

None of these is a full anticipation of any claim; the JP '296 (force-sensor-output correction) is the one warranting a closer § 102/§ 103 read if a machine translation were obtained.

4. Non-patent literature cited (2)

1. "Virtual Compliance Control of Multiple Degree of Freedom Robot," Digests of the Society of Instrument and Control Engineers, Japanese issue Vol. 22, No. 3 (March 1986), pp. 343–349. This is the source of Equation (1) quoted in the patent's own Background ([M] virtual mass, [K] virtual spring constant, [C] virtual viscosity). The patent expressly states this art assumes q ≈ Q and neglects the [m]·acceleration inertia term — i.e., the paper teaches away from the claimed correction. It therefore cannot anticipate any claim; it is the acknowledged problem statement.
2. "Robot Manipulators: Mathematics, Programming, and Control," Richard P. Paul, the MIT Press (cover only; record also spells the author "Rehard P. Paul"). General textbook reference for the position/attitude control loop. No § 102 relevance to the inertia-subtraction feature.

5. Conclusion — most relevant prior art and § 102 outcome

No cited reference anticipates any of claims 1–22. Under pre‑AIA § 102, anticipation requires a single reference disclosing every limitation. Each independent claim (1, 7, 14, 19, 20, 22) requires a second sense means that senses the inertia force on the end effector and control means that subtract that sensed inertia force from the sensed force/torque. Not one cited patent, foreign document, or NPL item discloses this combination. The references collectively supply only the force/torque-sensing and force-based joint-control environment (first sense means), vision/position-sensing alternatives (dependent claims), or generic dynamic-inertia modeling.

Ranking of the closest/most relevant art (all § 103 starting points, not § 102 anticipations):

1. US 4,621,332 A (Sugimoto et al., Hitachi) — the acknowledged force-compliance foundation; discloses force sensor + mass/spring/viscosity impedance control. Closest single reference.
2. US 4,243,923 A (Whitney et al., MIT) — force/torque feedback with an explicit arm inertia matrix in the model, but no sensed-inertia subtraction.
3. US 4,603,284 A (Perzley, Unimation) — compliant-motion control built on load/inertia modeling.
4. US 4,547,858 A (Horak, Allied) — manipulator-inertia compensation via nonlinear dynamics.
5. JP S60‑52296 A (Hitachi, 1985) — "correcting force sensor output," the closest foreign item on the correction concept.

Discrepancy flag (per my cross-reference instruction): The earlier Litigation summary stated the JP counterpart expires "…/JP2713899B2… not_active Expired – Fee Related," consistent with the record here; nothing in the prior-art set contradicts the earlier section. Note one record-level inconsistency worth flagging: the Google Patents structured data labels US 4,621,332 with priority "1983‑06‑20" while its U.S. filing is 1984‑06‑18 — both predate the critical date, so it is § 102(b)/(a) art either way and the inconsistency does not affect the outcome.

Practical caveat: This analysis rests on the citation list carried on the patent's own front page plus the sources above. A definitive § 102/§ 103 nullity or validity opinion would require full texts (and, for the Japanese items, verified translations) of the references — particularly JP S60‑52296 and the 1986 Virtual Compliance Control paper — which the indexed record does not reproduce in full.

I'll ground this analysis in the prior-art references listed on the patent page. Let me verify the key references.

Key prior art confirmed. Let me verify the remaining high-value references.

Let me verify the space-robotics and vision references.

Obviousness Analysis — U.S. Patent No. 4,906,907 under 35 U.S.C. § 103

Patent: U.S. 4,906,907 ("Robot system") · Hitachi, Ltd. · Inventors Tsuchihashi & Takarada
Priority 1987‑03‑30 (JP 62‑74001) · Filed 1988‑03‑30 · Granted 1990‑03‑06
Governing law: Pre‑AIA § 103(a) (application filed before 2013‑03‑16). KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), applies to pre‑AIA patents.

Note on continuity with prior work: the previously generated Litigation Report found no litigation on this patent. That is a litigation finding and does not bear on prior-art status; I am not repeating it here. One cross‑reference point is worth flagging because it matters for § 103: the report identified that later patents cite 4,906,907 as prior art, which confirms the reference is cited-by-others as a teaching in the field but says nothing about its own patentability. No contradiction exists between the sections.

1. The claim set and the actual point of novelty

22 claims; six independents: 1, 7, 14, 19, 20, 22.

The core insight, stated by the patent itself (Background, quoting its own Eq. (2)):

$$Q = q + [m]\frac{d^2x}{dt^2}$$

The patent's sole inventive contribution is the recognition that the force sensor output Q is corrupted by the inertial term $[m]d^2x/dt^2$, and that subtracting a sensed inertia force recovers the pure external force q. Everything else in the independent claims (six‑axis arm, joint servos, wrist‑mounted force sensor, compliance control) is admitted prior art in the "BACKGROUND OF THE INVENTION."

Critical observation for § 103: the claims are purely functional as to the inertia sensing ("means for sensing an inertia force") and recite nothing about how the inertia is sensed or how the mass/inertia values are obtained. The specification discloses three distinct physical realizations (acceleration sensor 119; vision system 501 + vision processor 502; joint position detectors 601–606 + sub‑controller 607) and a genuinely detailed unknown‑mass identification procedure (moving the manipulator and sampling several points to compute m, I'x, I'y, I'z immediately after grasping). That identification procedure is not in any claim. Its absence is what makes the claims broadly read on the prior art.

2. The prior-art universe, as listed on this page

All references below are taken from the patent's own Patent Citations (13), Family Cites Families (6), Non‑Patent Citations (4), and Similar Documents sections.

2a. Examiner‑cited U.S. patents (§ 102(b)/102(e) prior art)

2b. Family cites — including the most damaging reference

2c. Non‑patent literature

2d. "Similar Documents" — an unusually strong same‑assignee reference

3. Grounds of rejection

Ground A — Claims 1, 6, 13, 14

US 4,621,332 (Sugimoto/Hitachi) in view of US 4,547,858 (Allied), further in view of JPS6052296A (Hitachi) and/or EP 0 177 919 B1 (Sugimoto/Hitachi)

Why claim 14 is placed here rather than treated separately: it is Ground A plus the Fig. 8 architecture of the specification. US 4,547,858 discloses that exact architecture (correction injected at the servo/power‑amplifier stage, bypassing the trajectory planner). This is the weakest independent claim in the set.

Ground B — Claims 2, 8, 15 (second sense means = an acceleration sensor)

Ground A + US 4,243,923 and/or US 4,533,167

Substituting a dedicated accelerometer for a computed acceleration is the paradigm of a predictable design choice:

• US 4,547,858 already contemplates "sensors detecting the position and motion of said links" including acceleration.
• US 4,243,923 (MIT) teaches servo‑controlled manipulation with conventional dynamic transducers.
• The specification's own Fig. 5 shows the accelerometer as a strain gauge 403 on an elastic beam 404 with a proof mass 405 — the same transducer technology as the force sensor, read by the same kind of bridge circuit (121–123). Combining two strain‑gauge bridges is a mere aggregation of known elements performing their known functions (MPEP 2144.04; KSR).

A person of ordinary skill would have had every reason to prefer a direct accelerometer over double differentiation of encoder signals, because differentiation amplifies encoder quantization noise — a well‑known trade‑off. Result: obvious.

Ground C — Claims 4, 10, 17 (position detectors + arithmetic unit)

Ground A + US 4,621,332's encoder PE + Paul (1981)

• US 4,621,332 discloses encoders PE at each articulation and a counter 28 converting them to joint angles, plus a unit converting the articulation angle to the orthogonal hand coordinate x.
• Paul (1981) — cited by the patent as the standard reference for the "commonly employed" control theory — teaches the Jacobian transform and the time‑derivation chain needed to obtain end‑effector velocity and acceleration from joint variables.
• The claim requires only "position detectors … and an arithmetic unit for effecting an arithmetic process on detected signals." Two successive differentiations of a position signal is not a patentable advance; the specification itself concedes it: "the sub‑controller 607 effects a transformation on positional information, which undergoes two operations of differentiation with respect to time."

Obvious.

Ground D — Claims 3, 9, 16 (vision system + vision processor)

Ground A + US 4,305,130 + US 4,380,696 + US 4,616,121 + US 4,675,502

• US 4,305,130 enables "a robot with vision to acquire, orient and transport workpieces."
• US 4,380,696 and US 4,616,121 teach imaging a moving tool/workpiece and correcting manipulator motion in real time — which requires extracting motion (hence velocity/acceleration) from successive images.
• US 4,675,502 teaches real‑time tracking control of a taught path.
• Paul (1981) supplies the kinematics for converting image‑derived position histories into velocity and acceleration — and claim 16 expressly recites exactly that: "the vision processor computes the velocity and the acceleration of the image."

Motivation: the patent's own Fig. 3 shows a vision system 501 already installed on the spacecraft for the robot's work tasks. Reusing an existing sensor suite instead of adding accelerometer mass and cabling to a space manipulator is a recognized, cost‑ and mass‑driven engineering motivation. Obvious.

Ground E — Claims 5, 11, 18 (integrated force + inertia sensor unit)

Ground A + US 4,533,167 + US 4,603,284 + US 4,243,923

Claim 5 requires only that the two sense means be "integrated in a single unit … connected between said robot and said hold means." Both are strain‑gauge‑on‑flexure devices (specification: force sensor 401 = strain gauge on a beam between outer and inner shells; accelerometer 402 = strain gauge 403 on elastic beam 404). Placing two transducers on the same mounting face at the same location (the specification itself rationalizes 118 and 119 as "disposed at the same location") is a predictable packaging choice reducing registration error, wiring, and mass. Wrist‑mounted force/compliance units are already known from US 4,603,284 and US 4,533,167. Obvious — this is KSR's "known technique to improve similar devices in the same way."

Ground F — Claims 7, 12, 20, 21 (the third sense means: base/robot inertia)

Ground A + DE 3244211 (ERNO) + US 4,661,032 + the patent's own admission

The motivation here is not weak, because the patent supplies it against itself:

"the signal includes the inertia force applied from the base, the inertia force due to the mass of the end effector, and the inertia force associated with the mass of an object held by the end effector."

Once the wrist sensor is known to be contaminated by base motion, mounting a second inertial sensor between the base and the root of the arm (claim 12) is a direct, predictable implementation of the stated problem. The specification puts sensor 120 exactly there, "between the first link of the robot and a base on which the robot hand is mounted."

Supporting art:

• DE 3244211 (ERNO, orbiter manipulator): an orbital remote‑controlled manipulator equipped with sensors and command modules "die durch Bestückung mit entsprechenden Sensoren eine direkte Rückkoppelung ermöglichen" (direct feedback). ⚠️ Caveat: the German text I retrieved is a modular structural description — it discloses the sensor/feedback architecture but no control law. Its § 103 value is as background establishing that orbital manipulators with direct force feedback were known and were expected to operate where the base is not inertially fixed.
• US 4,661,032 teaches transforming sensed forces into a common operating‑space coordinate system — the same step the specification performs to produce "a force (torque) signal 305 in accordance with the coordinate system fixed to the base."
• US 4,547,858 computes link dynamics with the origin at the base and the motion of the third link expressed in link coordinates — i.e., accounts for base‑frame motion.
• The patent's own three‑signal decomposition (308 = M₁A₁, 309 = M₂A₁, 310 = M₁A₂) is straightforward linear algebra once both bodies' accelerations are measured: the cross‑terms M₂A₁ and M₁A₂ are exactly the couplings a skilled artisan writes down from Paul's Newton‑Euler recursion.

Obvious.

Ground G — Claims 19, 20, 22 ("in a microgravity condition")

Grounds A and F, applied a fortiori

Claims 19, 20 and 22 are word‑for‑word identical in their bodies to claims 1, 7 and 14 respectively; the only differences are (i) the preamble "in a microgravity condition" and (ii) "hold means" → "gripper means" (an obvious equivalent — the specification uses "gripper," "hand," "end effector" and "hold means" interchangeably throughout).

A preamble reciting the environment of use does not patentably distinguish a claim where the structure and the steps are unchanged: In re Schreiber, 377 F.2d 203 (CCPA 1967); MPEP 2111.02 and 2141.02. The claims are apparatus claims; nothing in the claim bodies changes as a function of gravity. If claims 1/7/14 fall, claims 19/20/22 fall with them.

Independent support (if the examiner treats the preamble as limiting): DE 3244211 establishes that orbital manipulator systems with sensor feedback were known, and the patent's own admission — "in the case of operation in an outer space, the inertia force exerted on the gripper cannot be neglected" — is a statement of the problem, not a solution. Recognizing that a correction is more necessary in microgravity is not invention; it is the recognition of the desirability of the very correction claimed.

4. Motivation to combine (KSR factors)

The combination is over‑determined. Each KSR factor is present:

1. Same field of endeavor. All references are robot manipulator control; the patent's art units confirm it (B25J 13/08 controls by sensing devices; B25J 13/085 force or torque sensors; B25J 13/088 position, velocity or acceleration sensors; B25J 9/16 program controls with "compensation for arm bending/inertia, pay load weight/inertia").
2. Same problem, explicitly articulated. The inventor states the problem as an equation (Q = q + [m]d²x/dt²) and then solves it by subtraction. Where the problem is articulated in the prior art or the background, the solution's obviousness is strengthened. MPEP 2144.04(II).
3. Same assignee and overlapping inventive entity — the strongest single motivation. US 4,621,332 (Sugimoto, Hitachi), US 4,620,436/EP 0 177 919 (Sugimoto & Hirabayashi, Hitachi), JPS6052296A ("Method of correcting force sensor output," Hitachi), JPS58206394 ("Robot position correction method," Hitachi) and the patent‑in‑suit (Tsuchihashi & Takarada, Hitachi) are all Hitachi. A corporation's own prior force‑sensor‑correction work is a compelling, non‑speculative motivation to combine; the inventors were working in the very laboratory line that produced it.
4. "Known technique to improve similar devices in the same way." KSR: "if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious unless its actual application is beyond his or her skill." Subtracting a known inertial term from a force measurement is arithmetic; nothing in the claims is beyond ordinary skill.
5. Predictable result. The relationship between acceleration, mass, and inertial force is linear, exact and universally understood (Newton's second law; Paul 1981). There is no unpredictability, no criticality of ranges, and no unexpected result in the claim scope.
6. Design incentive / recognized need. 1980s space‑station robotics (Fig. 3's spacecraft; DE 3244211's orbital manipulator) made microgravity force control a pressing, recognized objective. A recognized long‑felt need, coupled with a known solution, favors obviousness.
7. The examiner already had the primary reference but not the combination. US 4,621,332 is on the face of US 4,906,907. So the correct § 103 inquiry is not "was Sugimoto new?" but "would it have been obvious to add an inertia‑sensing means to Sugimoto's force‑controlled wrist?" The art above (US 4,547,858's explicit inertial‑torque computation; Paul's dynamics; Hitachi's own force‑sensor‑output‑correction work) answers that affirmatively.

5. Anticipated counterarguments and why they fail

6. Secondary considerations (objective indicia)

The record on this page contains no evidence of nexus, commercial success, copying, industry praise, or licensing. Two points cut against patentability:

• The genuinely non‑trivial subject matter was left unclaimed. The specification's most interesting disclosure is the post‑grasp, multi‑sample identification of unknown M₁ (m = F'/a′; I'x = M'x/α'x, etc., with averaging across several sampling points). Because no claim recites this, it cannot supply patentability for the claims as issued. Claim 1's "second sense means" is a § 112(f)-style functional recitation whose disclosed structures (accelerometer; vision system + processor; joint position detectors + arithmetic unit) are individually conventional in the robotics art.
• Broad, function‑only claim drafting makes the claims read on any implementation that (1) measures force at the wrist, (2) obtains an inertia force somehow, and (3) subtracts. That breadth is the reason the prior‑art combinations above reach the claims.

Argue in response: microgravity‑specific long‑felt need and failure of others (the prior literature's neglect of the inertia term) could support non‑obviousness — but that argument is weakened because (a) the patent's own background attributes the neglect to the small‑mass case rather than to inability, and (b) contemporaneous space‑robotics work (DE 3244211; the published literature in the patent's own citation list) shows the field was actively addressing manipulator dynamics in non‑terrestrial conditions.

7. Assessment summary and confidence

Overall: I would expect claims 1, 2, 4, 6, 8, 10, 13, 14, 15, 17 to be invalid as obvious on the strongest Ground A/B/C read, with 7, 12, 20, 21 (base inertia) and the vision claims 3, 9, 16 being closer calls that depend on how the third sense means and the "image processor" are construed and on whether the examiner accepts the DE 3244211 motivation.

Explicit caveats — I will not overstate:

1. I do not have full‑text claim‑level verification of US 4,243,923, US 4,273,920, US 4,303,130, US 4,380,696, US 4,533,167, US 4,603,284, US 4,530,062, US 4,616,121, US 4,675,502, US 4,761,596. My propositions about them rest on their titles, assignees, and standard knowledge of the art. Any of these could be materially stronger or weaker than I have characterized.
2. JPS6052296A ("Method of correcting force sensor output," Hitachi, 1985‑03‑25) is the single most promising reference in the list and the one I could least verify — I retrieved only its bibliographic record, not its text. If its disclosure turns out to be gravity/inertia compensation of a multi‑axis force sensor, Ground A strengthens substantially; if it concerns only thermal drift or strain‑gauge bridge correction, Ground A weakens and shifts weight to US 4,621,332 + US 4,547,858. This deserves a full‑text retrieval before any rejection is finalized.
3. DE 3244211 is a structural/modular disclosure; I am using it only as background establishing known orbital sensor‑feedback manipulators, not as teaching the claimed subtraction.
4. I have not performed a full prior‑art search beyond the patent's own citation list. The strongest unexplored candidate is US 4,620,436 / EP 0 177 919 (Sugimoto & Hirabayashi, Hitachi — force sensor transformation matrix calibration, listed on this page under Similar Documents), which computes the force at a wrist force sensor from encoder‑derived posture plus known masses and would reinforce Ground A/C substantially.
5. This is an analytical assessment of prior art, not a legal opinion on validity or infringement.