{"id":"fc10c2a8-2880-4fe4-82f8-c710eb82c0e9","arxiv_id":"2604.17245","paper_version":1,"verdict":"CONDITIONAL","confidence":"LOW","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"MM-Hand presents a modular 21-DOF dexterous hand with remote tendon actuation, integrated multimodal sensing, and open-source hardware that achieves 25 N fingertip force over 1 m transmission distance.","lead":"MM-Hand is a 21-DOF robotic hand that relocates motors to a remote base using tendon-sheath transmission, freeing space in the fingers and palm for modular 3D-printed structures, quick connectors, and multimodal sensors including joint angles, tactile feedback, motor data, and in-palm stereo vision. This approach aims to reduce hand mass, heat buildup, and maintenance issues while supporting high-force dexterous tasks.","discovery_kind":"new_method","skeptic_critique":{"model":"grok-4.3","headline":"Tendon-sheath friction losses and length variations lack explicit quantitative bounds under dynamic arm motion, leaving closed-loop control predictability unverified across operating regimes.","rationale":"The reader's weakest assumption directly identifies the same gap in quantitative validation of friction and length effects under motion. Because the abstract and experiments are described at a high level without the missing bounds, the concern is load-bearing for the headline performance claims. No other internal inconsistency or unsupported derivation appears in the given material.","tokens_in":1791,"tokens_out":346,"duration_ms":33611,"concrete_test":"From the full manuscript, extract the measured tendon force transmission ratio (motor torque to fingertip force) and the joint-angle RMSE during the arm-motion closed-loop trials at the highest reported speed and payload; if efficiency falls below 40 % or RMSE exceeds 4° without additional compensation, the 25 N practical-capacity claim and control reliability require qualification.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim is that remote 1 m tendon-sheath transmission still delivers practical 25 N fingertip force and supports reliable closed-loop joint control even while the arm moves. The manuscript states that length variation and friction are analyzed to guide routing, motor hub, and control design, and that closed-loop tracking was tested with both static and moving arm. However, the provided results give no measured transmission efficiency, no friction coefficient or loss percentage as a function of sheath curvature or velocity, and no position-error statistics attributable to length change during arm motion. Without these numbers it is impossible to confirm that the effects remain small enough and predictable enough for the claimed control performance to hold outside the specific test trajectories shown.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript presents MM-Hand, a 21-DOF multi-modal modular dexterous robotic hand using remote tendon-driven actuation with 1 m sheaths to relocate motors away from the hand. It describes spring-return fingers, modular 3D-printed structures, quick tendon connectors, and a multimodal sensing suite (joint angles, tactile, motor feedback, in-palm stereo vision). The authors analyze tendon-sheath length variation and friction loss to guide routing, motor hub, and closed-loop control design, then report experiments claiming 25 N fingertip force and successful joint-level command tracking under both static and moving-arm conditions. All hardware designs and software are released open-source.","tokens_in":1933,"tokens_out":432,"duration_ms":36252,"significance":"If the performance claims are substantiated with quantitative bounds, the work supplies a lightweight, maintainable, sensor-rich open-source platform that directly addresses mass, heat, and space limitations of conventional in-hand actuation for dexterous manipulation research.","major_comments":[{"comment":"Abstract and Experiments section: the claim of reliable closed-loop joint control during arm motion rests on the assertion that length variation and friction remain manageable, yet no measured transmission efficiency, friction loss percentage as a function of sheath curvature or velocity, or position-error statistics attributable to length change are provided; without these data the predictability of the controller outside the specific test trajectories cannot be verified.","section":"Abstract and Experiments"},{"comment":"Experiments section: the reported 25 N fingertip force under 1 m remote transmission lacks accompanying details on measurement protocol, number of trials, error bars, or comparison to direct-drive baselines, which is load-bearing for the central claim of practical load capacity.","section":"Experiments"}],"minor_comments":[{"comment":"The abstract states that closed-loop tracking was tested with both static and moving arm but does not specify the number of trials, trajectory types, or quantitative tracking metrics (e.g., RMSE values).","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the constructive and detailed feedback on our manuscript. We address each major comment below and have incorporated revisions to strengthen the presentation of our experimental results and analysis.","responses":[{"response":"We appreciate this observation. Our analysis of tendon-sheath length variation and friction loss was used to inform the routing design and controller parameters, and the closed-loop experiments demonstrated reliable tracking under both static and dynamic arm conditions. However, we agree that explicit quantitative measurements of transmission efficiency versus curvature/velocity and associated position-error statistics would better substantiate generalizability. In the revised manuscript we will add these data from additional characterization experiments, including efficiency curves and error statistics broken down by trajectory type.","revision_made":"yes","referee_comment":"[Abstract and Experiments] Abstract and Experiments section: the claim of reliable closed-loop joint control during arm motion rests on the assertion that length variation and friction remain manageable, yet no measured transmission efficiency, friction loss percentage as a function of sheath curvature or velocity, or position-error statistics attributable to length change are provided; without these data the predictability of the controller outside the specific test trajectories cannot be verified."},{"response":"We agree that the force results require more supporting detail to be fully convincing. The 25 N value was obtained with a calibrated load cell at the fingertip under quasi-static conditions with the 1 m sheath routing; the value represents the mean across repeated trials. In the revised Experiments section we will include the complete measurement protocol, number of trials, standard deviations, and a direct comparison against an equivalent direct-drive configuration to quantify the transmission penalty.","revision_made":"yes","referee_comment":"[Experiments] Experiments section: the reported 25 N fingertip force under 1 m remote transmission lacks accompanying details on measurement protocol, number of trials, error bars, or comparison to direct-drive baselines, which is load-bearing for the central claim of practical load capacity."}],"tokens_in":1450,"tokens_out":420,"duration_ms":35191,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"This paper describes MM-Hand, a 21 degree of freedom robotic hand that uses remote tendon actuation to keep motors out of the hand itself. The design includes modular 3D-printed parts, quick connectors for tendons, and a multimodal sensing setup with joint sensors, tactile feedback, motor info, and stereo vision in the palm. They open-sourced the hardware and software, which is a real plus for the field. What they do well is show that you can get decent force output—25N at the fingertip—even with a meter-long tendon sheath. They analyzed length variations and friction to set up the routing and control, and ran tests for both static and moving arm scenarios. The modularity and maintainability address common complaints about dexterous hands being hard to work with. The weaker part is the evidence around closed-loop performance during arm motion. The abstract talks about analyzing friction and length changes and testing tracking, but it doesn't provide specific measurements like efficiency losses or error stats linked to the motion. Without those, it's tough to see how predictable the system stays outside the exact tests shown. The force numbers are solid, but the control claims could use more backing. This work is aimed at people in dexterous manipulation research who want a ready-to-use, sensor-heavy platform rather than starting from zero. It builds on existing tendon-driven ideas but packages them nicely with the sensing and openness. I think it deserves peer review. The hardware contribution is concrete and the open-source release means others can verify and extend it, even if some experimental details need tightening.","headline":"MM-Hand is a practical open-source 21-DOF hand with remote actuation and rich sensing that hits useful force levels, though its dynamic control results need tighter quantitative support on transmission effects.","tokens_in":2480,"tokens_out":396,"would_cite":false,"duration_ms":35070,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Remote tendon actuation packs 21 degrees of freedom and 25N fingertip force into a lightweight dexterous hand with rich sensing.","keywords":["dexterous robotic hand","remote tendon actuation","tendon-driven","multimodal sensing","modular design","21-DOF","fingertip force"],"falsifier":"A test that records fingertip force falling below twenty newtons or joint tracking errors rising sharply after repeated arm motions that flex the one-meter sheaths through many different curvatures.","tokens_in":2693,"feed_emoji":"🤖","tokens_out":530,"duration_ms":52172,"temperature":0.7,"pith_summary":"The paper develops a robotic hand that moves its drive motors far away using tendon sheaths instead of placing them inside the hand. This choice frees space for twenty-one total degrees of freedom across the fingers and palm, plus multiple sensors and modular parts that can be swapped quickly. The authors measure how sheath length and friction change with motion, then apply that information to design routing paths and a joint controller that works while the arm moves. Experiments confirm that the fingertip still produces twenty-five newtons of force through a one-meter transmission and that the joints follow commands accurately in both fixed and moving conditions. The complete hardware and software are released so others can use the hand for manipulation research.","feed_headline":"Remote actuation delivers 21-DOF hand with 25N fingertip force","feed_subtitle":"Tendon sheaths move motors away from the hand to free space for sensors and modular parts while retaining usable strength over meter-long 1m","key_machinery":"Remote tendon-sheath actuation with spring-return fingers and quantitative analysis of length variation plus friction loss that permits motors to sit outside the hand.","core_discovery":"MM-Hand realizes a 21-DOF multi-modal modular dexterous hand through remote tendon-driven actuation with spring-return fingers, quick tendon connectors, and a sensing system that includes joint angle sensors, tactile sensors, motor-side feedback, and in-palm stereo vision. Analysis of tendon-sheath length variation and friction loss informs the routing, motor hub, and closed-loop control design. Experiments establish that the system transmits twenty-five newtons at the fingertip over one meter and maintains command tracking both with a static arm and during arm motion.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["21-DOF modular dexterous hand uses remote tendon actuation","Remote actuation supports 21-DOF MM-Hand with 25N force","MM-Hand integrates 21 DOF sensing via remote tendon drive","Multimodal 21-DOF hand with remote actuation and 25N output","Tendon sheaths enable 21-DOF dexterous hand design"],"cache_read_input_tokens":64,"weakest_assumption_plain":"Friction losses and length changes in the tendon sheaths remain predictable and compensable enough for closed-loop control when the arm moves and bends the routing paths.","fun_headline_variants_meta":{"raw":{"variants":["21-DOF modular dexterous hand uses remote tendon actuation","Remote actuation supports 21-DOF MM-Hand with 25N force","MM-Hand integrates 21 DOF sensing via remote tendon drive","Multimodal 21-DOF hand with remote actuation and 25N output","Tendon sheaths enable 21-DOF dexterous hand design"]},"model":"grok-4.3","cost_usd":0.010688,"raw_usage":{"total_tokens":4691,"prompt_tokens":778,"num_sources_used":0,"completion_tokens":94,"cost_in_usd_ticks":106878000,"prompt_tokens_details":{"text_tokens":778,"audio_tokens":0,"image_tokens":0,"cached_tokens":64},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":3819,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":778,"tokens_out":94,"duration_ms":58701,"temperature":1.0,"reasoning_tokens":3819,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-10T06:16:27.018224+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A test that records fingertip force falling below twenty newtons or joint tracking errors rising sharply after repeated arm motions that flex the one-meter sheaths through many different curvatures.","supporting_citations":[],"review_version":1}