Customized six axis robotic arm controller
Summary
Domain Medical Device
Skills Micro-controller Programming, Electronics, Understanding of Servo motors, Mathematics, Mechanical
Team Size Self (outsourced PCB manufacturing to another company)
Duration 1.5 Month (including time to get the PCB Manufactured)

Objective: For one of the medical device a six axis robotic arm was required. While the controllers were available off the shelf, minimizing BOM was one of the primary objective. Hence there was a need design in-house six axis controller.

Challenges:
  1. There were three makes of servo motors that needed to be made compatible with the controller
  2. Some motors required 24V and some required 5 volt signal input.
  3. The IO's across the motors were mixed requiring pull-up to pull-down.
  4. Precision of less than 0.1 mm was required in the movements.
  5. To minimize BOM, servo motors with relative encoders were used. Homing was a major issue.
  6. All the axis used gears. Hence, homing was not straight forward.

Solution: After trying NXP and STM32, finally selected STM32 micro controller. It allowed greater speed so that complex mathematical calculations could be achieved without creating delay in the movement. Spent quite a lot of time in pin assignments as well as schematics for the circuits. Finally designed the board along with the software to take command through RS232 and then move the Robot as per the commend.