I don't know if there is a straightforward answer to this question. I could not find much with google.
To give context, I am building a self balancing robot. It balances pretty well, but I am struggling to eliminate small oscillations around the balanced point. Looking at plots of PWM voltage and motor speed shows the culprit is that small voltage commands from the controller have no effect when the motors are stationary. The integral term in the PID increases the command until the motor starts, but then it goes too fast causing overshoot of the balanced position. The same process then repeats with a small negative command. I use 12V motors and they do not start below 6V.
Since the robot mainly operates near its balanced point, the controller spends most of its time issuing small fine control commands, which are completely ignored. The plot shows that the integral term causes the controller to ramp to the breakaway torque and then shortly after switch to the negative breakaway torque. The fancy pants PID is acting like it has just 3 voltages; 0, +breakaway and -breakaway !
I believe that the current gear ratio of 75:1 is far too high, and believe that using a lower ratio will reduce the starting voltage. Is that correct ?
Since the current motors seem to have more than enough torque, I am considering switching to a 34:1 gearbox, and I am hoping that might roughly halve the starting voltage, but without knowing the relationship between gear ratio and breakaway torque I am just guessing.
To give context, I am building a self balancing robot. It balances pretty well, but I am struggling to eliminate small oscillations around the balanced point. Looking at plots of PWM voltage and motor speed shows the culprit is that small voltage commands from the controller have no effect when the motors are stationary. The integral term in the PID increases the command until the motor starts, but then it goes too fast causing overshoot of the balanced position. The same process then repeats with a small negative command. I use 12V motors and they do not start below 6V.
Since the robot mainly operates near its balanced point, the controller spends most of its time issuing small fine control commands, which are completely ignored. The plot shows that the integral term causes the controller to ramp to the breakaway torque and then shortly after switch to the negative breakaway torque. The fancy pants PID is acting like it has just 3 voltages; 0, +breakaway and -breakaway !
I believe that the current gear ratio of 75:1 is far too high, and believe that using a lower ratio will reduce the starting voltage. Is that correct ?
Since the current motors seem to have more than enough torque, I am considering switching to a 34:1 gearbox, and I am hoping that might roughly halve the starting voltage, but without knowing the relationship between gear ratio and breakaway torque I am just guessing.