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Improve wheel rpm calculation #313

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Sep 1, 2022
Merged

Improve wheel rpm calculation #313

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39 changes: 22 additions & 17 deletions UE4Project/Plugins/AirSim/Source/Vehicles/Car/CarPawnSimApi.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ void CarPawnSimApi::createVehicleApi(ACarPawn* pawn, const msr::airlib::GeoPoint
//these are called on render ticks
void CarPawnSimApi::updateRenderedState(float dt)
{
updateWheelStates(dt);
updateWheelStates();
updateKinematics(dt);
vehicle_api_->getStatusMessages(vehicle_api_messages_);

Expand Down Expand Up @@ -596,29 +596,34 @@ float computeAngleChange(float prev_rotation_angle_rad, float new_rotation_angle
return new_rotation_angle_rad + (new_rotation_angle_rad > prev_rotation_angle_rad ? 0.0f : 2.0f * M_PI) - prev_rotation_angle_rad;
}

void CarPawnSimApi::updateWheelStates(float dt)
void CarPawnSimApi::updateWheelStates()
{
wheel_states_->time_stamp = msr::airlib::ClockFactory::get()->nowNanos();

physx::PxVehicleWheelsDynData& mWheelsDynData = movement_->PVehicle->mWheelsDynData;

const float unreal_rotation_angle_to_radians = (2 * M_PI) / -1800.0;
const float unreal_steering_angle_to_radians = (M_PI) / 180.0;
const float radians_per_second_to_rpm = 60.0 / (2 * M_PI);

//update kinematics from pawn's movement instead of physics engine
float fl_new_rotation_angle_rad = movement_->Wheels[0]->GetRotationAngle() * unreal_rotation_angle_to_radians;
float fr_new_rotation_angle_rad = movement_->Wheels[1]->GetRotationAngle() * unreal_rotation_angle_to_radians;
float rl_new_rotation_angle_rad = movement_->Wheels[2]->GetRotationAngle() * unreal_rotation_angle_to_radians;
float rr_new_rotation_angle_rad = movement_->Wheels[3]->GetRotationAngle() * unreal_rotation_angle_to_radians;

wheel_states_->fl.rpm = 0.3 * wheel_states_->fl.rpm + 0.7 * computeAngleChange(wheel_states_->fl.rotation_angle, fl_new_rotation_angle_rad) / dt * radians_per_second_to_rpm;
wheel_states_->fr.rpm = 0.3 * wheel_states_->fr.rpm + 0.7 * computeAngleChange(wheel_states_->fr.rotation_angle, fr_new_rotation_angle_rad) / dt * radians_per_second_to_rpm;
wheel_states_->rl.rpm = 0.3 * wheel_states_->rl.rpm + 0.7 * computeAngleChange(wheel_states_->rl.rotation_angle, rl_new_rotation_angle_rad) / dt * radians_per_second_to_rpm;
wheel_states_->rr.rpm = 0.3 * wheel_states_->rr.rpm + 0.7 * computeAngleChange(wheel_states_->rr.rotation_angle, rr_new_rotation_angle_rad) / dt * radians_per_second_to_rpm;

wheel_states_->fl.rotation_angle = fl_new_rotation_angle_rad;
wheel_states_->fr.rotation_angle = fr_new_rotation_angle_rad;
wheel_states_->rl.rotation_angle = rl_new_rotation_angle_rad;
wheel_states_->rr.rotation_angle = rr_new_rotation_angle_rad;
// at very low velocities the angular velocity becomes very unstable,
// so a higher smoothing factor is needed to obtain a usable estimate
float higher_smoothing_factor_rpm_threshold = 80;
float avg_rear_wheel_rpm = (wheel_states_->rr.rpm + wheel_states_->rl.rpm) / 2;
float rpm_smoothing_coeff = 0.7;
if (avg_rear_wheel_rpm < higher_smoothing_factor_rpm_threshold) {
rpm_smoothing_coeff = 0.9;
}

wheel_states_->fl.rpm = wheel_states_->fl.rpm * (rpm_smoothing_coeff) + (1 - rpm_smoothing_coeff) * OmegaToRPM(mWheelsDynData.getWheelRotationSpeed(0));
wheel_states_->fr.rpm = wheel_states_->fl.rpm * (rpm_smoothing_coeff) + (1 - rpm_smoothing_coeff) * OmegaToRPM(mWheelsDynData.getWheelRotationSpeed(1));
wheel_states_->rl.rpm = wheel_states_->fl.rpm * (rpm_smoothing_coeff) + (1 - rpm_smoothing_coeff) * OmegaToRPM(mWheelsDynData.getWheelRotationSpeed(2));
wheel_states_->rr.rpm = wheel_states_->fl.rpm * (rpm_smoothing_coeff) + (1 - rpm_smoothing_coeff) * OmegaToRPM(mWheelsDynData.getWheelRotationSpeed(3));

wheel_states_->fl.rotation_angle = mWheelsDynData.getWheelRotationAngle(0);
wheel_states_->fr.rotation_angle = mWheelsDynData.getWheelRotationAngle(1);
wheel_states_->rl.rotation_angle = mWheelsDynData.getWheelRotationAngle(2);
wheel_states_->rr.rotation_angle = mWheelsDynData.getWheelRotationAngle(3);

wheel_states_->fl.steering_angle = movement_->Wheels[0]->GetSteerAngle() * unreal_steering_angle_to_radians;
wheel_states_->fr.steering_angle = movement_->Wheels[1]->GetSteerAngle() * unreal_steering_angle_to_radians;
Expand Down
2 changes: 1 addition & 1 deletion UE4Project/Plugins/AirSim/Source/Vehicles/Car/CarPawnSimApi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -160,7 +160,7 @@ class CarPawnSimApi : public msr::airlib::VehicleSimApiBase
void plot(std::istream& s, FColor color, const Vector3r& offset);
CarPawnSimApi::Pose toPose(const FVector& u_position, const FQuat& u_quat) const;
void updateKinematics(float dt);
void updateWheelStates(float dt);
void updateWheelStates();
void setStartPosition(const FVector& position, const FRotator& rotator);
private:
Params params_;
Expand Down