diff options
Diffstat (limited to 'src/modules/systemlib/pid/pid.c')
-rw-r--r-- | src/modules/systemlib/pid/pid.c | 111 |
1 files changed, 42 insertions, 69 deletions
diff --git a/src/modules/systemlib/pid/pid.c b/src/modules/systemlib/pid/pid.c index 77c952f52..cab33282c 100644 --- a/src/modules/systemlib/pid/pid.c +++ b/src/modules/systemlib/pid/pid.c @@ -39,7 +39,7 @@ /** * @file pid.c * - * Implementation of generic PID control interface. + * Implementation of generic PID controller. * * @author Laurens Mackay <mackayl@student.ethz.ch> * @author Tobias Naegeli <naegelit@student.ethz.ch> @@ -53,24 +53,21 @@ #define SIGMA 0.000001f -__EXPORT void pid_init(PID_t *pid, float kp, float ki, float kd, float intmax, - float limit, uint8_t mode, float dt_min) +__EXPORT void pid_init(PID_t *pid, uint8_t mode, float dt_min) { - pid->kp = kp; - pid->ki = ki; - pid->kd = kd; - pid->intmax = intmax; - pid->limit = limit; pid->mode = mode; pid->dt_min = dt_min; - pid->count = 0.0f; - pid->saturated = 0.0f; - pid->last_output = 0.0f; - pid->sp = 0.0f; - pid->error_previous = 0.0f; + pid->kp = 0.0f; + pid->ki = 0.0f; + pid->kd = 0.0f; pid->integral = 0.0f; + pid->integral_limit = 0.0f; + pid->output_limit = 0.0f; + pid->error_previous = 0.0f; + pid->last_output = 0.0f; } -__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float intmax, float limit) + +__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float integral_limit, float output_limit) { int ret = 0; @@ -95,15 +92,15 @@ __EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float ret = 1; } - if (isfinite(intmax)) { - pid->intmax = intmax; + if (isfinite(integral_limit)) { + pid->integral_limit = integral_limit; } else { ret = 1; } - if (isfinite(limit)) { - pid->limit = limit; + if (isfinite(output_limit)) { + pid->output_limit = output_limit; } else { ret = 1; @@ -112,42 +109,18 @@ __EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float return ret; } -//void pid_set(PID_t *pid, float sp) -//{ -// pid->sp = sp; -// pid->error_previous = 0; -// pid->integral = 0; -//} - -/** - * - * @param pid - * @param val - * @param dt - * @return - */ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, float dt) { - /* error = setpoint - actual_position - integral = integral + (error*dt) - derivative = (error - previous_error)/dt - output = (Kp*error) + (Ki*integral) + (Kd*derivative) - previous_error = error - wait(dt) - goto start - */ - if (!isfinite(sp) || !isfinite(val) || !isfinite(val_dot) || !isfinite(dt)) { return pid->last_output; } float i, d; - pid->sp = sp; - // Calculated current error value - float error = pid->sp - val; + /* current error value */ + float error = sp - val; - // Calculate or measured current error derivative + /* current error derivative */ if (pid->mode == PID_MODE_DERIVATIV_CALC) { d = (error - pid->error_previous) / fmaxf(dt, pid->dt_min); pid->error_previous = error; @@ -167,39 +140,39 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo d = 0.0f; } - if (pid->ki > 0.0f) { - // Calculate the error integral and check for saturation - i = pid->integral + (error * dt); + /* calculate PD output */ + float output = (error * pid->kp) + (d * pid->kd); - if ((pid->limit > SIGMA && (fabsf((error * pid->kp) + (i * pid->ki) + (d * pid->kd)) > pid->limit)) || - fabsf(i) > pid->intmax) { - i = pid->integral; // If saturated then do not update integral value - pid->saturated = 1; + if (pid->ki > SIGMA) { + /* calculate error integral and check for saturation */ + float i = pid->integral + (error * dt); - } else { - if (!isfinite(i)) { - i = 0.0f; - } + /* fail-safe */ + if (!isfinite(i)) { + i = 0.0f; + } + + if ((pid->output_limit > SIGMA && (fabsf(output + (i * pid->ki)) > pid->output_limit)) || + fabsf(i) > pid->integral_limit) { + /* saturated, do not update integral value */ + i = pid->integral; + } else { pid->integral = i; - pid->saturated = 0; } - } else { - i = 0.0f; - pid->saturated = 0; + /* add I component to output */ + output += i * pid->ki; } - // Calculate the output. Limit output magnitude to pid->limit - float output = (error * pid->kp) + (i * pid->ki) + (d * pid->kd); - + /* limit output */ if (isfinite(output)) { - if (pid->limit > SIGMA) { - if (output > pid->limit) { - output = pid->limit; + if (pid->output_limit > SIGMA) { + if (output > pid->output_limit) { + output = pid->output_limit; - } else if (output < -pid->limit) { - output = -pid->limit; + } else if (output < -pid->output_limit) { + output = -pid->output_limit; } } @@ -212,5 +185,5 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo __EXPORT void pid_reset_integral(PID_t *pid) { - pid->integral = 0; + pid->integral = 0.0f; } |