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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?

Thank you

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  • $\begingroup$ What bus voltage and current do you need. $\endgroup$
    – hauptmech
    Oct 13 '18 at 23:19
  • $\begingroup$ motors are 12v with 5amp rated current. stall current is around 35 amps. $\endgroup$
    – KalanaRatnayake
    Oct 14 '18 at 4:13
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You can often find used or surplus industrial controllers capable of current control for good prices, including your range. Elmo Motion Control and Copley Control both have controllers with a small volume that are often surplused. There are even dual and triple drive products.

Ebay and Ali Express are easy places to start looking but more local sources can also be found if you look, no matter which country you are in.

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  • $\begingroup$ I looked up elmo motion control in ebay as you said. they are called servo drivers. this is a problem i had for a long time, "Can i hookup a dc geared motor directly to a SERVO Drive or do i need additional hardware?". (i know that hobby servos are dc geared motors with a potentiometer for position. that why i asked this) $\endgroup$
    – KalanaRatnayake
    Oct 14 '18 at 4:18
  • $\begingroup$ You will need to check the manual of each drive to confirm, but yes, servo drives designed for brushless motor can be configured to drive brushed motors. I have done this with the elmo whistle drives. $\endgroup$
    – hauptmech
    Oct 14 '18 at 11:45

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