Estimated_current and velocity mode: high current at standstill

dekutree64 · July 10, 2026, 5:43pm

Hmm, you may have found a true bug in the PID.

src/common/pid.cpp

0de7d5aba


      
              timestamp_prev = timestamp_now;
          }
          
          // u(s) = (P + I/s + Ds)e(s)
          // Discrete implementations
          // proportional part
          // u_p  = P *e(k)
          float proportional = P * error;
          // Tustin transform of the integral part
          // u_ik = u_ik_1  + I*Ts/2*(ek + ek_1)
          float integral = integral_prev + I*dt*0.5f*(error + error_prev);
          // antiwindup - limit the output
          if(_isset(limit)) integral = _constrain(integral, -limit, limit);
          // Discrete derivation
          // u_dk = D(ek - ek_1)/Ts
          float derivative = D*(error - error_prev)/dt;
          
          // sum all the components
          float output = proportional + integral + derivative;
          // antiwindup - limit the output variable
          if(_isset(limit)) output = _constrain(output, -limit, limit);

Since error and prev_error should both be zero, integral just gets set to integral_prev, i.e. it’s probably sitting there non-zero commanding torque, but since the motor is unable to move due to stiction/cogging, nothing ever causes it to change. But it looks like it’s been that way since the beginning, so I don’t know how it could have gone unnoticed for so long, nor do I have enough experience with PID controllers to propose a solution.

Try printing out motor.PID_Velocity.integral_prev to verify this is the problem. Comment out protected: on line 41 of pid.h so all the variables are accessible by outside code.