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Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Wed Oct 09, 2024 4:43 pm
by dubois35
I don't think that's quite right, for what it's worth.
Tendon-driven fingers let you move the heavier actuators back into the palm or forearm, keeping the fingers themselves light and fast, but they introduce cable routing, tensioning, and long-term wear problems that direct-actuated fingers don't have. Figure's fourth-generation Dexterous Hand (on Figure 02/03) reportedly offers 16 degrees of freedom per hand with sensors integrated into each finger, aimed at fine force control tasks like handling small electronic components without crushing them.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Sat Oct 12, 2024 8:28 am
by kwilliams
Small correction on one detail:
A lot of the manipulation shown in production demos still leans heavily on teleoperation, particularly for anything involving fine force control or novel objects - autonomous grasp success rates on genuinely unstructured, previously-unseen clutter are still well below what teleoperation can achieve.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Tue Oct 15, 2024 12:37 am
by williams84
@kwilliams This lines up with my experience.
Figure's fourth-generation Dexterous Hand (on Figure 02/03) reportedly offers 16 degrees of freedom per hand with sensors integrated into each finger, aimed at fine force control tasks like handling small electronic components without crushing them.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Tue Oct 22, 2024 11:57 pm
by choi98
@williams84 Short answer:
Palm sensing gets less attention than fingertip sensing, but a lot of power grasps (holding a box, a tool handle) rely more on palm and lateral finger contact than fingertip contact, so under-sensing the palm can leave a real blind spot in grasp confidence.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Thu Oct 31, 2024 9:04 am
by kwilliams
@choi98 Ran into exactly this myself.
Underactuated hands (fewer actuators than joints, using mechanical coupling to shape the grasp) are a reasonable engineering compromise for robust power grasps on a budget, but they generally can't do fine in-hand manipulation the way a fully actuated hand can.
Totally unrelated but has anyone else noticed how fast component costs are dropping this year.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Mon Nov 11, 2024 3:20 pm
by jhansen
@kwilliams Counterpoint:
Wet, oily, or otherwise low-friction objects are still a genuine edge case for most current hands, since tactile sensing and grasp-force controllers are typically tuned and validated on dry, higher-friction test objects.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Fri Nov 22, 2024 12:26 am
by zoeanderson
Short answer:
Imitation learning from human demonstration video (without robot teleoperation data) is an appealing way to scale up training data cheaply, but it runs into the embodiment gap - human hand kinematics and force profiles don't map directly onto a robot hand's very different mechanism.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Tue Nov 26, 2024 4:24 am
by scott21
@zoeanderson Here's the relevant bit as far as I understand it:
Grasp planning for deformable or non-rigid objects (bags, cables, cloth) remains one of the genuinely unsolved problems in manipulation - rigid-body grasp models simply don't capture how the object will behave once contact starts.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Fri Dec 06, 2024 8:08 pm
by ethan_fisc
New to this, so forgive me if this is obvious -
Palm sensing gets less attention than fingertip sensing, but a lot of power grasps (holding a box, a tool handle) rely more on palm and lateral finger contact than fingertip contact, so under-sensing the palm can leave a real blind spot in grasp confidence. Figure's fourth-generation Dexterous Hand (on Figure 02/03) reportedly offers 16 degrees of freedom per hand with sensors integrated into each finger, aimed at fine force control tasks like handling small electronic components without crushing them.
Re: Tendon-driven vs direct-actuated fingers - reliability in practice?
Posted: Sun Dec 08, 2024 5:22 am
by nicole57
Ran into exactly this myself.
Compliant wrists that absorb impact during a bad approach or misjudged contact reduce mechanical stress on the whole arm, which matters a lot for long-term reliability even though it's a less visible feature than the hand itself.