DC motor control with TM4C123. Each board controls 2 motors independently and can talk to other boards
- A base module for a differential drive robot.
- SCARA-like robot (combine two modules).
- TM4C123 MCU
- TB6612FNG motor controller
- 2 channel encoder interface
- 2 channel 1A continuous, 1.3A max
- CAN Bus interface
- UART interface
- PID control library
PID control library
The PID control library incorporates the use of an autotuning mechanism using the Nelder-Mead method whereby it searches through R3 space using a simplex model to reduce the scoring function, which in this case is the time it takes to settle.
There are some drawbacks using the Nelder-Mead method because the quality of the search depends on the initial values.
The modifiable values for the PID control library are:
- gen_algo.c->testArray ~ This array stores 4 initial points (P,I,D) to search
- gen_algo.h->TEST_PERIOD ~ This value is the length of time in cycles to measure the PID response
- motor.h->MAX_PWM ~ the maximum PWM counts. The range of PWM is from 0 to this value
- motor.h->TIME_TO_COUNT ~ the time to count the velocity. The encoder interface will wait this length of time to determine the velocity
Useful Function Descriptions
- absolute_to_relative: takes a value from an absolute sensor (orientation/counts) and converts it to a relative value.
- pid_controller: takes a sensed value and attempts to match it with a given desired value. Includes testing and autotuning algorithms.
- pid_autotune: auto-tunes the PID values.
- setSpeed: sets the speed of the motor based on the pwm counts given.
- getMotorXCounts: gets the counts from the encoder interface, note that absolute_to_relative function is already applied here
- getMotorXVelocity: gets the velocity in counts/time from the QEI interface
- zeroMotorX: zeros the motors and the relative counts
- initAll: calls all the configuration options
- uartRead: given a char pointer and length to read, reads from UART
- uartWrite: writes from a char pointer
- CAN bus interface not fully implemented yet