{"id":6722,"date":"2016-10-16T10:58:27","date_gmt":"2016-10-16T08:58:27","guid":{"rendered":"http:\/\/www.swisswuff.ch\/tech\/?p=6722"},"modified":"2019-12-01T14:24:26","modified_gmt":"2019-12-01T12:24:26","slug":"trs-prehensor-grip-surface-tweaking","status":"publish","type":"post","link":"https:\/\/www.swisswuff.ch\/tech\/?p=6722","title":{"rendered":"TRS Prehensor [grip surface tweaking]"},"content":{"rendered":"

The TRS Prehensor<\/a> [manufacturer> TRS<\/a>] is a great gripper, and recently smoked all myoelectric competition (at a prosthetic arm side by side race at the “Cybathlon”, a public Circus event that the NCCR Robotics held for reasons that so far are not entirely understood at least from a prosthetic hand\/arm user view<\/a>).<\/p>\n

A week has gone by since then, and still no public statement of the NCCR robotics organizers<\/a> as to why body powered arm technology performed so much better than they anticipated, and worse, still no cogent clever research program drafted to successfully address prosthetic arm issues<\/a>. Not a single tweet by Professor Riener and his team containing #cybathlon and #trsprehensor – so, in all sports and fairness, we are probably done with assuming this was all about sports. It wasn’t, and the communications very clearly show that.<\/p>\n

The biggest issue at this moment for robotic researchers now may probably be: why is this possible? What happened? Can we lay down the reasons for that? Because keeping on missing out on any deeper understanding there will likely cause similar problems in the future – and we do not want that again, do we. There are deeply intriguing answers to these pressing questions. It is just that who has time to wait for these people! What takes them so long!<\/p>\n

“I waited for 30 years for robot engineers to build me a prosthetic arm so I could finally clean up my house. It became a real mess during all these years. Three decades is a long time, you know.” – Anonymous<\/em><\/p>\n

No peace for the wicked.<\/p>\n

And so to clean up the house today, I used the TRS Prehensor. I massively intensified using it for many tasks since then<\/a>. Now, I always like to use these opportunities to troubleshoot grips<\/a> and see where I go with the result.<\/p>\n

Wowoweewa!<\/p>\n

<\/p>\n

As no product ever is absolutely perfect, the ones that can be tuned, the ones that can be bent, and loved into submission are the ones that end up being perfect.<\/p>\n

As is, the TRS Prehensor has quite rigid PU claws. Most of you probably never cared to really look, leave alone ordering one so you could get a first hand understanding. But, trust me on that, it is quite rigid at its gripper surface.<\/p>\n

As all material choices, there are advantages and disadvantages. The PU material used there is great on one hand as the harder the gripper material, the longer it lasts. However, the harder PU surfaces also cause a bit of a slip, particularly for objects with limited or no elasticity or deformability, and do not grip very small (and particularly hard) objects too well. Conversely, softer surfaces get used up, damaged, worn down faster, so they require a swap faster.<\/p>\n

From a manufacturing view, you must keep the stability and robustness, material wise, of your gripper product at a reasonable maximum while making sure that the soft grip parts, the consumables so to say, can be replaced and swapped by the consumer or user at minimal efforts and minimal cost. Otherwise, you will lose them, simple as that.<\/p>\n

The TRS Prehensor most certainly is a very, very mature product with refined features.But that does not mean we can not take this even further. With just two gripper claws and a\u00a0 four extension protrusion set on the fixed upper claw (see photos below), the technical requirements are all there to approximate an insanely wicked technical grip type embodied by the infamous bean bag gripper: using soft and mildly adhesive surface deformation to one’s advantage while ice skating on the pre-configured grip reliability already built into the TRS Prehensor.<\/p>\n