pybricks.common.Motor: Restore duty_limit behavior.

This is an alternate way to use temporary limits in pbio (no nlr buf)
but without a breaking change in the definition of duty limit or stall.

See pybricks/support#1069

CHANGELOG.md

@@ -17,8 +17,6 @@
 
 ### Changed
 - Updated MicroPython to v1.20.0.
-- Changed `duty_limit` argument of `Motor.run_until_stalled` to `torque_limit`.
-  The original name continues to work as well.
 
 ### Fixed
 - Fixed stdin containing `0x06` command byte ([support#1052]).

lib/pbio/include/pbio/servo.h

@@ -161,7 +161,7 @@ pbio_error_t pbio_servo_stop(pbio_servo_t *srv, pbio_control_on_completion_t on_
 pbio_error_t pbio_servo_reset_angle(pbio_servo_t *srv, int32_t reset_angle, bool reset_to_abs);
 pbio_error_t pbio_servo_run_forever(pbio_servo_t *srv, int32_t speed);
 pbio_error_t pbio_servo_run_time(pbio_servo_t *srv, int32_t speed, uint32_t duration, pbio_control_on_completion_t on_completion);
-pbio_error_t pbio_servo_run_until_stalled(pbio_servo_t *srv, int32_t speed, int32_t torque_limit_pct, pbio_control_on_completion_t on_completion);
+pbio_error_t pbio_servo_run_until_stalled(pbio_servo_t *srv, int32_t speed, int32_t torque_limit, pbio_control_on_completion_t on_completion);
 pbio_error_t pbio_servo_run_angle(pbio_servo_t *srv, int32_t speed, int32_t angle, pbio_control_on_completion_t on_completion);
 pbio_error_t pbio_servo_run_target(pbio_servo_t *srv, int32_t speed, int32_t target, pbio_control_on_completion_t on_completion);
 pbio_error_t pbio_servo_track_target(pbio_servo_t *srv, int32_t target);

lib/pbio/src/servo.c

@@ -101,8 +101,16 @@ static pbio_error_t pbio_servo_update(pbio_servo_t *srv) {
         // Get required feedforward torque for current reference
         feedforward_torque = pbio_observer_get_feedforward_torque(srv->observer.model, ref.speed, ref.acceleration);
 
+        // HACK: Constrain total torque to respect temporary duty_cycle limit.
+        // See https://github.com/pybricks/support/issues/1069.
+        // The feedback torque is already constrained by the temporary limit,
+        // and this would be enough in a run_until_overload-like scenario. But
+        // for now we must limit the feedforward torque also, or it would never
+        // get into the stall state at high speeds.
+        int32_t total_torque = pbio_int_math_clamp(feedback_torque + feedforward_torque, srv->control.settings.actuation_max_temporary);
+
         // Actuate the servo. For torque control, the torque payload is passed along. Otherwise payload is ignored.
-        err = pbio_servo_actuate(srv, requested_actuation, feedback_torque + feedforward_torque);
+        err = pbio_servo_actuate(srv, requested_actuation, total_torque);
         if (err != PBIO_SUCCESS) {
             return err;
         }
@@ -647,12 +655,11 @@ pbio_error_t pbio_servo_run_time(pbio_servo_t *srv, int32_t speed, uint32_t dura
  *
  * @param [in]  srv                 The servo instance.
  * @param [in]  speed               Angular velocity in degrees per second.
- * @param [in]  torque_limit_pct    Percentage of maximum feedback torque to use.
- *                                  It will still use the default feedforward torque.
+ * @param [in]  torque_limit        Maximum torque to use.
  * @param [in]  on_completion       What to do once stalled.
  * @return                          Error code.
  */
-pbio_error_t pbio_servo_run_until_stalled(pbio_servo_t *srv, int32_t speed, int32_t torque_limit_pct, pbio_control_on_completion_t on_completion) {
+pbio_error_t pbio_servo_run_until_stalled(pbio_servo_t *srv, int32_t speed, int32_t torque_limit, pbio_control_on_completion_t on_completion) {
 
     if (on_completion == PBIO_CONTROL_ON_COMPLETION_CONTINUE) {
         // Can't continue after stall.
@@ -673,7 +680,7 @@ pbio_error_t pbio_servo_run_until_stalled(pbio_servo_t *srv, int32_t speed, int3
     srv->control.type |= PBIO_CONTROL_TYPE_FLAG_OBJECTIVE_IS_STALL;
 
     // Set the temporary torque limit used during this maneuver.
-    srv->control.settings.actuation_max_temporary = srv->control.settings.actuation_max * torque_limit_pct / 100;
+    srv->control.settings.actuation_max_temporary = torque_limit;
 
     return PBIO_SUCCESS;
 }

pybricks/common/pb_type_motor.c

@@ -265,25 +265,22 @@ STATIC mp_obj_t common_Motor_run_until_stalled(size_t n_args, const mp_obj_t *po
         common_Motor_obj_t, self,
         PB_ARG_REQUIRED(speed),
         PB_ARG_DEFAULT_OBJ(then, pb_Stop_COAST_obj),
-        PB_ARG_DEFAULT_NONE(torque_limit),
         PB_ARG_DEFAULT_NONE(duty_limit));
 
     mp_int_t speed = pb_obj_get_int(speed_in);
     pbio_control_on_completion_t then = pb_type_enum_get_value(then_in, &pb_enum_type_Stop);
 
-    // Backwards compatibility <= v3.2: allow duty_limit arg as torque_limit.
+    // REVISIT: Use torque limit. See https://github.com/pybricks/support/issues/1069.
+    int32_t torque_limit;
     if (duty_limit_in != mp_const_none) {
-        torque_limit_in = duty_limit_in;
-    }
-
-    // Get torque limit as percentage of max torque.
-    int32_t torque_limit_pct = 100;
-    if (torque_limit_in != mp_const_none) {
-        torque_limit_pct = pb_obj_get_pct(torque_limit_in);
+        int32_t voltage_limit = pbio_battery_get_voltage_from_duty_pct(pb_obj_get_pct(duty_limit_in));
+        torque_limit = pbio_observer_voltage_to_torque(self->srv->observer.model, voltage_limit);
+    } else {
+        torque_limit = self->srv->control.settings.actuation_max;
     }
 
     // Start moving.
-    pb_assert(pbio_servo_run_until_stalled(self->srv, speed, torque_limit_pct, then));
+    pb_assert(pbio_servo_run_until_stalled(self->srv, speed, torque_limit, then));
 
     // Handle completion by awaiting or blocking.
     return pb_type_awaitable_await_or_wait(