Robots might use servo motors or even solenoids , but there is a much better way , but it is not easy to empliment , mechanically .
Your old VW had a Beilstein jack . Using springs and the above method to quickly lock movement , in a robot , can be impressive .
We have all seen the Honda robot . Maybe they use this methodology , i dont know .
very large solenoids and very fast locking , can give very fast and accurate response .
Solenoids must be driven with efficient "buck" regulators . They are oscillating types , the bipolar transistor is driven by the same coil that it is driving . They approach 95% eff ' They can deliver a 25 amp pulse in microseconds You could create PWM , with them .
They are so fast , if an arm had such a drive , you could maybe teach your robot to "box" ( as a pugilist .) The springs are what improve the efficiency . if you had no springs to store this quick energy , then you circuit must waste energy "controlling"
Common buck regulators , waste drive to the bipolar transistor , but my circuit adds another winding to drive the base of B' T' . The free running freq is above 400 Khz . This means , when you enable it , the B' T' turns on very fast and then saturates the core and shuts down , but it starts up again , since its an oscillator . The simple control pulls the coil to ground and "sets" the output DC voltage .
This circuit is far simpler and safer than even the LM494 used in IBM PC pow supplies , because it saturates the ferrite core . But there is no future for the old non-saturating core , I.C. controlled , pow supplies . even in Flour' lites , they dumped the controller I.C. and instead osc' it and saturate the core .
Emmiter is output , so the base drive coil , can fully saturate the B'T' , wastes less heat ..
If you try to store energy in air , you will waste too much heat . Springs work well , dont get hot .
The next problem is , compound eyes . I remember seeing a I.C. that had a array a hole cut in the top of an early DRAM memory .