From: Geoffrey B. <g....@au...> - 2005-07-06 11:57:39
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Daniel Aarno wrote: > This is a valid point. However, in practice one often starts by moving > the arm to a predefined "safe" position using joint control and then > goes on with pose control. I think controlling the same physical device > through several interfaces might bring more problems than it is worth. > An other aproach would be to leave joint commands out completely and use > "raw" commands as suggested by Geoffrey earlier, since all joint control > will be arm-specific. I agree that switching between joint and IK control would be problematic with two separate interfaces. I wasn't sure how common an occurance it was, though. While joint control will be arm-configuration specific, it won't be control method specific, so I think there is good enough reason to put generic "make joint X go to position Y" commands in. Chances are high that in the future a lot of arms made by different people will have the same configuration. Also remember that we want to be able to get information about the joints in the arm back, allowing clients to enumerate the capabilities of the arm they've found and adapt how they treat it accordingly. This sort of flexibility in client software is, I think, of vital importance to writing better, longer-lasting robot software. My supervisor just suggested that the end effector orientation could be altered by using the Goto command and supplying the current position, and have the driver check if the position has changed from the current enough to warrent the use of IK for full arm movement. One thing that occurs to me about specifically re-orienting the end effector, and thus makes me wonder about the usefulness of such a feature, is that the position of the end effector is (as far as I know) usually taken about some centroid or similar, whereas reorienting it without using IK would mean movement about the base of the end effector; not quite the same thing. If IK is going to be involved no matter what, you may as well just send another Goto command. Geoff |