I'm currently working on a robotics project where i have to build a quadruped. i have somewhat finished the designing for the time being and now moving into simulations. I have followed a inverse dynamics approach to build the controller of the leg following this blog and i have added,
Torque = Jacobean' * force
equation to the control equation in order to exert required reaction force and other forces. Meanwhile i have to order required parts to build a model early on due to delivery time. i selected PMDC to control the robot but have been restricted to cheap ones since the budget is low.
The problem is selecting a controller circuit. Since the control signal from the dynamics model outputs a torque value and since DC motor torque is proportional to current, i understand that i have to control the current of the motor. But all the motor controllers i found in USD 1-100 range only controls speed(Voltage) of the motor. The cheapest one i found is dual motor controller for USD 100. But it is out of my reach because i have to control 12 dc motors. what are the options i have?
1) can i achieve this by modifying a general motor controller? or is there a controller i can use in USD 1-50 range?
2) i looked in sparkfun, pololu sites for no success. but robotpower.com had a board called megamoto which i came across but doesn't say that i can current control using this. anyone who has experience with this?
3) Can anyone give me a schematic for a simple motor controller that can control the current. (i understand that i can achieve this by using mosfets, gate driver ics, shunt resistors and current sense amplifiers but doesn't have much knowledge regarding the selection of components or designing of motor controllers.
4) are there any other methods to approach this?