AP_MotorsUGV: steering limits and constraint done by each output handler

each motor output handler (regular, skid, omni) becomes responsible for constraining the steering input (if required) and setting the limits flags
it is possible to reduce duplicate code but I think it might be more important to keep it clear which level is responsible for the limiting and constraining of steering

APMrover2/AP_MotorsUGV.cpp

@@ -161,7 +161,7 @@ void AP_MotorsUGV::setup_servo_output()
 //   no scaling by speed or angle should be performed
 void AP_MotorsUGV::set_steering(float steering, bool apply_scaling)
 {
-    _steering = constrain_float(steering, -4500.0f, 4500.0f);
+    _steering = steering;
     _scale_steering = apply_scaling;
 }
 
@@ -230,9 +230,6 @@ void AP_MotorsUGV::output(bool armed, float ground_speed, float dt)
     // sanity check parameters
     sanity_check_parameters();
 
-    // clear and set limits based on input (limit flags may be set again by output_regular or output_skid_steering methods)
-    set_limits_from_input(armed, _steering, _throttle);
-
     // slew limit throttle
     slew_limit_throttle(dt);
 
@@ -465,6 +462,13 @@ void AP_MotorsUGV::output_regular(bool armed, float ground_speed, float steering
         }
     }
 
+    // clear and set limits based on input
+    // we do this here because vectored thrust or speed scaling may have reduced steering request
+    set_limits_from_input(armed, steering, throttle);
+
+    // constrain steering
+    steering = constrain_float(steering, -4500.0f, 4500.0f);
+
     // always allow steering to move
     SRV_Channels::set_output_scaled(SRV_Channel::k_steering, steering);
 }
@@ -475,6 +479,13 @@ void AP_MotorsUGV::output_omni(bool armed, float steering, float throttle, float
     if (!has_lateral_control()) {
         return;
     }
+
+    // clear and set limits based on input
+    set_limits_from_input(armed, steering, throttle);
+
+    // constrain steering
+    steering = constrain_float(steering, -4500.0f, 4500.0f);
+
     if (armed) {
         // scale throttle, steering and lateral to -1 ~ 1
         const float scaled_throttle = throttle / 100.0f;
@@ -527,6 +538,12 @@ void AP_MotorsUGV::output_skid_steering(bool armed, float steering, float thrott
         return;
     }
 
+    // clear and set limits based on input
+    set_limits_from_input(armed, steering, throttle);
+
+    // constrain steering
+    steering = constrain_float(steering, -4500.0f, 4500.0f);
+
     // handle simpler disarmed case
     if (!armed) {
         if (_disarm_disable_pwm) {