• aditya mehrotra.

joint velocities vs. actuator velocities [robotics to-know]

So I came across something in my 2.12 pset today worth pointing out. The idea of joint velocities vs actuator velocities. Because YES, they are different. At first, I looked at this system and was like "how can the joint velocities and actuator velocities be different?"

But notice this robot... so for this robot we don't just directly say the velocity of the joint is the same as the actuator velocity especially in the case of joint 2. So, let's say actuator three turns and we are using PID Velocity Control or something and actuator 2 remains stationary, right? What this results in is the joint 2 rotating because the actuator is moving but the belt stationary so the belt is moving relative to the actuator which means the joint is actually rotation even if the actuator is NOT, theta_2 is changing!

So the velocity of actuator two also needs to compensate for BOTH the velocity of the joint 2 we want, but also the fact that it is moving with respect to how theta_3 is changing!

Some interesting that I wanted to keep because it's pretty important especially for the bio-inspired, low-inertia robotics we want to do.

#robotics #omgrobots #essentials #jacobians #math #reference_frames

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