It's unfortunate that we still don't have cheap torque controlled robot actuators. Controlling force rather than position led to a drastic improvement in walking robots. I would also highly recommend using something beefier than an arduino to control a walking robot as most approaches to walking robots today rely on performing fast optimization. MIT's minicheetah has used a control approach that involves simulating the robot about 0.5 seconds into the future 50 times a second.
We actually have very cheap and pretty powerful position-controlled actuators (hobby servo motors). Attach any kind of spring and displacement measurement device (potentiometer, hall sensor, optical, LVDT, etc) and voila, instant torque controlled actuator.
You can look up Series Elastic Actuators for more info or use this article as guidance (any spring will do as long as the force range and spring constant is adequate).
The servo they use is $493[0], at that price I wouldn't necessarily consider it a hobby servo. The control for that specific series elastic servo needs some work. There have been other attempts at making cheap series elastic actuators. An interesting one was the programmable spring work[2][3]. Although one problem with series elastic actuators is that they can be difficult to control because of the compliance. Force servos were also an interesting attempt at doing cheap force control[4] and by using load cells they avoided the compliance problem. Unfortunately, force servos did not have any position control.
It is also possible to use current sensing to measure torque.
ODrive + brushless + encoder (~150€ per axis) can provide current measurements, though you may need to create some PID loop.
If the brushless solution is still too expensive. You can use 775 brushed motors + encoder + BTS 7960 driver + (optional gearbox) (They have current sensing by using additional resistance (Edit:and RC filter) ) (10€-50€ per axis from china). Although that's not powerful enough for jumping robots.
I do agree, this is one of the many improvementents/experimentation the project needs. Actually, the Minitaur example come with a torque controller implementation (https://github.com/bulletphysics/bullet3/blob/master/example...), needs tests. btw I'm going to use a Jetson mini as controller!! :)
In interaction with anything rigid (or even deformable), position control does not mean anything. Force (or torque) control defines the actual physical interaction.
I don't see any of those videos actually demonstrating Spot Mini walking successfully. Some comments suggest that the motors are not strong enough, or the body is too heavy.
I've seen a crawling robot trained with a string which would pull it back to the starting position after each episode so it could automatically try over and over again. I'd love to see someone doing that with a biped and just lift it up on a hoist to reset its orientation and position whenever it fell over. But really, it might not make a lot of economic sense if you can simulate the physics like these guys are doing.
Thanks! I'm currently working on the 'knowledge transfer', the aim is to build an almost-real-time controller for the robot - I'll probably start with a web app. Any contribution is welcomed!! :)