ardupilot/libraries/AP_Motors/AP_MotorsHeli_Dual.cpp

/*
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <AP_HAL/AP_HAL.h>
#include "AP_MotorsHeli_Dual.h"
#include <GCS_MAVLink/GCS.h>

extern const AP_HAL::HAL& hal;

const AP_Param::GroupInfo AP_MotorsHeli_Dual::var_info[] = {
    AP_NESTEDGROUPINFO(AP_MotorsHeli, 0),

    // Indices 1-6 were used by servo position params and should not be used

    // Indices 7-8 were used by phase angle params and should not be used

    // @Param: DUAL_MODE
    // @DisplayName: Dual Mode
    // @Description: Sets the dual mode of the heli, either as tandem, transverse, or intermeshing/coaxial.
    // @Values: 0:Longitudinal, 1:Transverse, 2:Intermeshing/Coaxial
    // @User: Standard
    AP_GROUPINFO("DUAL_MODE", 9, AP_MotorsHeli_Dual, _dual_mode, AP_MOTORS_HELI_DUAL_MODE_TANDEM),

    // @Param: DCP_SCALER
    // @DisplayName: Differential-Collective-Pitch Scaler
    // @Description: Scaling factor applied to the differential-collective-pitch
    // @Range: 0 1
    // @User: Standard
    AP_GROUPINFO("DCP_SCALER", 10, AP_MotorsHeli_Dual, _dcp_scaler, AP_MOTORS_HELI_DUAL_DCP_SCALER),

    // @Param: DCP_YAW
    // @DisplayName: Differential-Collective-Pitch Yaw Mixing
    // @Description: Feed-forward compensation to automatically add yaw input when differential collective pitch is applied.  Disabled for intermeshing mode.
    // @Range: -10 10
    // @Increment: 0.1
    // @User: Standard
    AP_GROUPINFO("DCP_YAW", 11, AP_MotorsHeli_Dual, _dcp_yaw_effect, 0),

    // @Param: YAW_SCALER
    // @DisplayName: Scaler for yaw mixing
    // @Description: Scaler for mixing yaw into roll or pitch.
    // @Range: -10 10
    // @Increment: 0.1
    // @User: Standard
    AP_GROUPINFO("YAW_SCALER", 12, AP_MotorsHeli_Dual, _yaw_scaler, 1.0f),

    // Indices 13-15 were used by RSC_PWM_MIN, RSC_PWM_MAX and RSC_PWM_REV and should not be used

    // @Param: COL2_MIN
    // @DisplayName: Swash 2 Minimum Collective Pitch
    // @Description: Lowest possible servo position in PWM microseconds for swashplate 2
    // @Range: 1000 2000
    // @Units: PWM
    // @Increment: 1
    // @User: Standard
    AP_GROUPINFO("COL2_MIN", 16, AP_MotorsHeli_Dual, _collective2_min, AP_MOTORS_HELI_DUAL_COLLECTIVE2_MIN),

    // @Param: COL2_MAX
    // @DisplayName: Swash 2 Maximum Collective Pitch
    // @Description: Highest possible servo position in PWM microseconds for swashplate 2
    // @Range: 1000 2000
    // @Units: PWM
    // @Increment: 1
    // @User: Standard
    AP_GROUPINFO("COL2_MAX", 17, AP_MotorsHeli_Dual, _collective2_max, AP_MOTORS_HELI_DUAL_COLLECTIVE2_MAX),

    // Indice 18 was used by COL2_MID and should not be used

    // Indice 19 was used by COL_CTRL_DIR and should not be used

    // @Param: SW_TYPE
    // @DisplayName: Swash 1 Type
    // @Description: H3 is generic, three-servo only. H3_120/H3_140 plates have Motor1 left side, Motor2 right side, Motor3 elevator in rear. HR3_120/HR3_140 have Motor1 right side, Motor2 left side, Motor3 elevator in front - use H3_120/H3_140 and reverse servo and collective directions as necessary. For all H3_90 swashplates use H4_90 and don't use servo output for the missing servo. For H4-90 Motors1&2 are left/right respectively, Motors3&4 are rear/front respectively. For H4-45 Motors1&2 are LF/RF, Motors3&4 are LR/RR 
    // @Values: 0:H3 Generic,1:H1 non-CPPM,2:H3_140,3:H3_120,4:H4_90,5:H4_45
    // @User: Standard

    // @Param: SW_COL_DIR
    // @DisplayName: Swash 1 Collective Direction
    // @Description: Direction collective moves for positive pitch. 0 for Normal, 1 for Reversed
    // @Values: 0:Normal,1:Reversed
    // @User: Standard

    // @Param: SW_LIN_SVO
    // @DisplayName: Linearize Swash 1 Servos
    // @Description: This linearizes the swashplate 1 servo's mechanical output to account for nonlinear output due to arm rotation.  This requires a specific setup procedure to work properly.  The servo arm must be centered on the mechanical throw at the servo trim position and the servo trim position kept as close to 1500 as possible. Leveling the swashplate can only be done through the pitch links.  See the ardupilot wiki for more details on setup.
    // @Values: 0:Disabled,1:Enabled
    // @User: Standard

    // @Param: SW_H3_ENABLE
    // @DisplayName: Swash 1 H3 Generic Enable
    // @Description: Automatically set when H3 generic swash type is selected for swashplate 1. Do not set manually.
    // @Values: 0:Disabled,1:Enabled
    // @User: Advanced

    // @Param: SW_H3_SV1_POS
    // @DisplayName: Swash 1 H3 Generic Servo 1 Position
    // @Description: Azimuth position on swashplate for servo 1 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW_H3_SV2_POS
    // @DisplayName: Swash 1 H3 Generic Servo 2 Position
    // @Description: Azimuth position on swashplate 1 for servo 2 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW_H3_SV3_POS
    // @DisplayName: Swash 1 H3 Generic Servo 3 Position
    // @Description: Azimuth position on swashplate 1 for servo 3 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW_H3_PHANG
    // @DisplayName: Swash 1 H3 Generic Phase Angle Comp
    // @Description: Only for H3 swashplate.  If pitching the swash forward induces a roll, this can be correct the problem
    // @Range: -30 30
    // @Units: deg
    // @User: Advanced
    // @Increment: 1
    AP_SUBGROUPINFO(_swashplate1, "SW_", 20, AP_MotorsHeli_Dual, AP_MotorsHeli_Swash),

    // @Param: SW2_TYPE
    // @DisplayName: Swash 2 Type
    // @Description: H3 is generic, three-servo only. H3_120/H3_140 plates have Motor1 left side, Motor2 right side, Motor3 elevator in rear. HR3_120/HR3_140 have Motor1 right side, Motor2 left side, Motor3 elevator in front - use H3_120/H3_140 and reverse servo and collective directions as necessary. For all H3_90 swashplates use H4_90 and don't use servo output for the missing servo. For H4-90 Motors1&2 are left/right respectively, Motors3&4 are rear/front respectively. For H4-45 Motors1&2 are LF/RF, Motors3&4 are LR/RR 
    // @Values: 0:H3 Generic,1:H1 non-CPPM,2:H3_140,3:H3_120,4:H4_90,5:H4_45
    // @User: Standard

    // @Param: SW2_COL_DIR
    // @DisplayName: Swash 2 Collective Direction
    // @Description: Direction collective moves for positive pitch. 0 for Normal, 1 for Reversed
    // @Values: 0:Normal,1:Reversed
    // @User: Standard

    // @Param: SW2_LIN_SVO
    // @DisplayName: Linearize Swash 2 Servos
    // @Description: This linearizes the swashplate 2 servo's mechanical output to account for nonlinear output due to arm rotation.  This requires a specific setup procedure to work properly.  The servo arm must be centered on the mechanical throw at the servo trim position and the servo trim position kept as close to 1500 as possible. Leveling the swashplate can only be done through the pitch links.  See the ardupilot wiki for more details on setup.
    // @Values: 0:Disabled,1:Enabled
    // @User: Standard

    // @Param: SW2_H3_ENABLE
    // @DisplayName: Swash 2 H3 Generic Enable
    // @Description: Automatically set when H3 generic swash type is selected for swashplate 2. Do not set manually.
    // @Values: 0:Disabled,1:Enabled
    // @User: Advanced

    // @Param: SW2_H3_SV1_POS
    // @DisplayName: Swash 2 H3 Generic Servo 1 Position
    // @Description: Azimuth position on swashplate for servo 1 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW2_H3_SV2_POS
    // @DisplayName: Swash 2 H3 Generic Servo 2 Position
    // @Description: Azimuth position on swashplate 2 for servo 2 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW2_H3_SV3_POS
    // @DisplayName: Swash 2 H3 Generic Servo 3 Position
    // @Description: Azimuth position on swashplate 2 for servo 3 with the front of the heli being 0 deg
    // @Range: -180 180
    // @Units: deg
    // @User: Advanced

    // @Param: SW2_H3_PHANG
    // @DisplayName: Swash 2 H3 Generic Phase Angle Comp
    // @Description: Only for H3 swashplate.  If pitching the swash forward induces a roll, this can be correct the problem
    // @Range: -30 30
    // @Units: deg
    // @User: Advanced
    // @Increment: 1
    AP_SUBGROUPINFO(_swashplate2, "SW2_", 21, AP_MotorsHeli_Dual, AP_MotorsHeli_Swash),

    // @Param: DCP_TRIM
    // @DisplayName: Differential Collective Pitch Trim
    // @Description: Removes I term bias due to center of gravity offsets or discrepancies between rotors in swashplate setup. If DCP axis has I term bias while hovering in calm winds, use value of bias in DCP_TRIM to re-center I term.
    // @Range: -0.2 0.2
    // @Increment: 0.01
    // @User: Standard
    AP_GROUPINFO("DCP_TRIM", 22, AP_MotorsHeli_Dual, _dcp_trim, 0.0f),

    // @Param: YAW_REV_EXPO
    // @DisplayName: Yaw reverser expo
    // @Description: For intermeshing mode only. Yaw revereser smoothing exponent, smoothen transition near zero collective region. Increase this parameter to shink smoothing range. Set to -1 to disable reverser. 
    // @Range: -1 1000
    // @Increment: 1.0
    // @User: Standard
    AP_GROUPINFO("YAW_REV_EXPO", 23, AP_MotorsHeli_Dual, _yaw_rev_expo, -1),

    AP_GROUPEND
};

// set update rate to motors - a value in hertz
void AP_MotorsHeli_Dual::set_update_rate( uint16_t speed_hz )
{
    // record requested speed
    _speed_hz = speed_hz;

    // setup fast channels
    uint32_t mask = _swashplate1.get_output_mask() | _swashplate2.get_output_mask();

    rc_set_freq(mask, _speed_hz);
}

// init_outputs
void AP_MotorsHeli_Dual::init_outputs()
{
    if (!initialised_ok()) {
        // set rotor servo range
        _main_rotor.init_servo();
    }

    set_initialised_ok(_frame_class == MOTOR_FRAME_HELI_DUAL);
}

// calculate_armed_scalars
void AP_MotorsHeli_Dual::calculate_armed_scalars()
{
    // Set rsc mode specific parameters
    if (_main_rotor._rsc_mode.get() == ROTOR_CONTROL_MODE_THROTTLECURVE || _main_rotor._rsc_mode.get() == ROTOR_CONTROL_MODE_AUTOTHROTTLE) {
        _main_rotor.set_throttle_curve();
    }
    // keeps user from changing RSC mode while armed
    if (_main_rotor._rsc_mode.get() != _main_rotor.get_control_mode()) {
        _main_rotor.reset_rsc_mode_param();
        _heliflags.save_rsc_mode = true;
    }
    // saves rsc mode parameter when disarmed if it had been reset while armed
    if (_heliflags.save_rsc_mode && !armed()) {
        _main_rotor._rsc_mode.save();
        _heliflags.save_rsc_mode = false;
    }

    if (_heliflags.in_autorotation) {
        _main_rotor.set_autorotation_flag(_heliflags.in_autorotation);
        // set bailout ramp time
        _main_rotor.use_bailout_ramp_time(_heliflags.enable_bailout);
    }else { 
        _main_rotor.set_autorotation_flag(false);
    }
}

// calculate_scalars
void AP_MotorsHeli_Dual::calculate_scalars()
{
    // range check collective min, max and mid
    if( _collective_min >= _collective_max ) {
        _collective_min.set(AP_MOTORS_HELI_COLLECTIVE_MIN);
        _collective_max.set(AP_MOTORS_HELI_COLLECTIVE_MAX);
    }


    // range check collective min, max and mid for rear swashplate
    if( _collective2_min >= _collective2_max ) {
        _collective2_min.set(AP_MOTORS_HELI_DUAL_COLLECTIVE2_MIN);
        _collective2_max.set(AP_MOTORS_HELI_DUAL_COLLECTIVE2_MAX);
    }

    _collective_zero_thrust_deg.set(constrain_float(_collective_zero_thrust_deg, _collective_min_deg, _collective_max_deg));

    _collective_land_min_deg.set(constrain_float(_collective_land_min_deg, _collective_min_deg, _collective_max_deg));

    if (!is_equal((float)_collective_max_deg, (float)_collective_min_deg)) {
        // calculate collective zero thrust point as a number from 0 to 1
        _collective_zero_thrust_pct = (_collective_zero_thrust_deg-_collective_min_deg)/(_collective_max_deg-_collective_min_deg);

        // calculate collective land min point as a number from 0 to 1
        _collective_land_min_pct = (_collective_land_min_deg-_collective_min_deg)/(_collective_max_deg-_collective_min_deg);
    } else {
        _collective_zero_thrust_pct = 0.0f;
        _collective_land_min_pct = 0.0f;
    }

    _collective2_zero_thrst_pct = _collective_zero_thrust_pct;

    // configure swashplate 1 and update scalars
    _swashplate1.configure();

    // configure swashplate 2 and update scalars
    _swashplate2.configure();

    // set mode of main rotor controller and trigger recalculation of scalars
    _main_rotor.set_control_mode(static_cast<RotorControlMode>(_main_rotor._rsc_mode.get()));
    calculate_armed_scalars();
}

// Mix and output swashplates for tandem
void AP_MotorsHeli_Dual::mix_tandem(float pitch_input, float roll_input, float yaw_input, float collective1_input, float collective2_input)
{
    // Differential cyclic roll is used for yaw and combined for roll
    const float swash1_roll = roll_input + _yaw_scaler * yaw_input;
    const float swash2_roll = roll_input - _yaw_scaler * yaw_input;

    // cyclic is not used for pitch control
    const float swash_pitch = 0.0;

    // Differential collective for pitch and combined for thrust
    const float swash1_coll =  0.45 * _dcp_scaler * (pitch_input + constrain_float(_dcp_trim, -0.2, 0.2)) + collective1_input;
    const float swash2_coll = -0.45 * _dcp_scaler * (pitch_input + constrain_float(_dcp_trim, -0.2, 0.2)) + collective2_input;

    // Calculate servo positions in swashplate library
    _swashplate1.calculate(swash1_roll, swash_pitch, swash1_coll);
    _swashplate2.calculate(swash2_roll, swash_pitch, swash2_coll);
}

// Mix and output swashplates for transverse
void AP_MotorsHeli_Dual::mix_transverse(float pitch_input, float roll_input, float yaw_input, float collective1_input, float collective2_input)
{
    // cyclic is not used for roll control
    const float swash_roll = 0.0;

    // Differential cyclic pitch is used for yaw
    const float swash1_pitch = pitch_input - _yaw_scaler * yaw_input;
    const float swash2_pitch = pitch_input + _yaw_scaler * yaw_input;

    // Differential collective for roll and combined for thrust
    const float swash1_coll =  0.45 * _dcp_scaler * (roll_input + constrain_float(_dcp_trim, -0.2, 0.2)) + collective1_input;
    const float swash2_coll = -0.45 * _dcp_scaler * (roll_input + constrain_float(_dcp_trim, -0.2, 0.2)) + collective2_input;

    // Calculate servo positions in swashplate library
    _swashplate1.calculate(swash_roll, swash1_pitch, swash1_coll);
    _swashplate2.calculate(swash_roll, swash2_pitch, swash2_coll);
}

// Mix and output swashplates for intermeshing
void AP_MotorsHeli_Dual::mix_intermeshing(float pitch_input, float roll_input, float yaw_input, float collective1_input, float collective2_input)
{
    // Direct roll control on both swash plates
    const float swash_roll = roll_input;

    // Differential cyclic pitch is used for yaw and combined for pitch
    const float swash1_pitch = pitch_input - _yaw_scaler * yaw_input;
    const float swash2_pitch = pitch_input + _yaw_scaler * yaw_input;

    // Differential collective for yaw and combined for thrust
    const float swash1_coll =   0.45 * _dcp_scaler * yaw_input + collective1_input;
    const float swash2_coll =  -0.45 * _dcp_scaler * yaw_input + collective2_input;

    // Calculate servo positions in swashplate library
    _swashplate1.calculate(swash_roll, swash1_pitch, swash1_coll);
    _swashplate2.calculate(swash_roll, swash2_pitch, swash2_coll);
}

// update_motor_controls - sends commands to motor controllers
void AP_MotorsHeli_Dual::update_motor_control(AP_MotorsHeli_RSC::RotorControlState state)
{
    // Send state update to motors
    _main_rotor.output(state);

    if (state == AP_MotorsHeli_RSC::RotorControlState::STOP) {
        // set engine run enable aux output to not run position to kill engine when disarmed
        SRV_Channels::set_output_limit(SRV_Channel::k_engine_run_enable, SRV_Channel::Limit::MIN);
    } else {
        // else if armed, set engine run enable output to run position
        SRV_Channels::set_output_limit(SRV_Channel::k_engine_run_enable, SRV_Channel::Limit::MAX);
    }

    // Check if rotors are run-up
    _heliflags.rotor_runup_complete = _main_rotor.is_runup_complete();
    // Check if rotors are spooled down
    _heliflags.rotor_spooldown_complete = _main_rotor.is_spooldown_complete();
}

//
// move_actuators - moves swash plate to attitude of parameters passed in
//                - expected ranges:
//                       roll : -1 ~ +1
//                       pitch: -1 ~ +1
//                       collective: 0 ~ 1
//                       yaw:   -1 ~ +1
//
void AP_MotorsHeli_Dual::move_actuators(float roll_out, float pitch_out, float collective_in, float yaw_out)
{
    // initialize limits flag
    limit.throttle_lower = false;
    limit.throttle_upper = false;

    if (_dual_mode == AP_MOTORS_HELI_DUAL_MODE_TRANSVERSE || _dual_mode == AP_MOTORS_HELI_DUAL_MODE_INTERMESHING) {
        if (pitch_out < -_cyclic_max/4500.0f) {
            pitch_out = -_cyclic_max/4500.0f;
            limit.pitch = true;
        }

        if (pitch_out > _cyclic_max/4500.0f) {
            pitch_out = _cyclic_max/4500.0f;
            limit.pitch = true;
        }
    } else {
        if (roll_out < -_cyclic_max/4500.0f) {
            roll_out = -_cyclic_max/4500.0f;
            limit.roll = true;
        }

        if (roll_out > _cyclic_max/4500.0f) {
            roll_out = _cyclic_max/4500.0f;
            limit.roll = true;
        }
    }

    // constrain collective input
    float collective_out = collective_in;
    if (collective_out <= 0.0f) {
        collective_out = 0.0f;
        limit.throttle_lower = true;
    }
    if (collective_out >= 1.0f) {
        collective_out = 1.0f;
        limit.throttle_upper = true;
    }

    // ensure not below landed/landing collective
    if (_heliflags.landing_collective && collective_out < _collective_land_min_pct) {
        collective_out = _collective_land_min_pct;
        limit.throttle_lower = true;
    }

    // updates below land min collective flag
    if (collective_out <= _collective_land_min_pct) {
        _heliflags.below_land_min_coll = true;
    } else {
        _heliflags.below_land_min_coll = false;
    }

    // updates takeoff collective flag based on 50% hover collective
    update_takeoff_collective_flag(collective_out);

    // Set rear collective to midpoint if required
    float collective2_out = collective_out;
    if (_servo_mode == SERVO_CONTROL_MODE_MANUAL_CENTER) {
        collective2_out = _collective2_zero_thrst_pct;
    }

    // if servo output not in manual mode, process pre-compensation factors
    if (_servo_mode == SERVO_CONTROL_MODE_AUTOMATED) {
        // add differential collective pitch yaw compensation
        float yaw_compensation = 0.0f;

        if (_dual_mode == AP_MOTORS_HELI_DUAL_MODE_INTERMESHING) {
            // for intermeshing, reverse yaw in negative collective region and smoothen transition near zero collective
            if (_yaw_rev_expo > 0.01f) {
                // yaw_compensation range: (-1,1) S-shaped curve (Logistic Model) 1/(1 + e^kt)
                yaw_compensation = 1.0f - (2.0f / (1.0f + powf(2.7182818f , _yaw_rev_expo * (collective_out-_collective_zero_thrust_pct))));
                yaw_out = yaw_out * yaw_compensation;
            }
        } else {
            if (_dual_mode == AP_MOTORS_HELI_DUAL_MODE_TRANSVERSE) {
                yaw_compensation = _dcp_yaw_effect * roll_out;
            } else { // AP_MOTORS_HELI_DUAL_MODE_TANDEM
                yaw_compensation = _dcp_yaw_effect * pitch_out;
            }
            yaw_out = yaw_out + yaw_compensation;
        }
    }

    // scale yaw and update limits
    if (yaw_out < -_cyclic_max/4500.0f) {
        yaw_out = -_cyclic_max/4500.0f;
        limit.yaw = true;
    }
    if (yaw_out > _cyclic_max/4500.0f) {
        yaw_out = _cyclic_max/4500.0f;
        limit.yaw = true;
    }

    // scale collective pitch for front swashplate (servos 1,2,3)
    float collective_scaler = ((float)(_collective_max-_collective_min))*0.001f;
    float collective_out_scaled = collective_out * collective_scaler + (_collective_min - 1000)*0.001f;

    // scale collective pitch for rear swashplate (servos 4,5,6)
    float collective2_scaler = ((float)(_collective2_max-_collective2_min))*0.001f;
    float collective2_out_scaled = collective2_out * collective2_scaler + (_collective2_min - 1000)*0.001f;

    // feed power estimate into main rotor controller
    // ToDo: add main rotor cyclic power?
    _main_rotor.set_collective(fabsf(collective_out));

    // Mix swash plate
    switch (_dual_mode) {
        case AP_MOTORS_HELI_DUAL_MODE_TANDEM:
        default:
            mix_tandem(pitch_out, roll_out, yaw_out, collective_out_scaled, collective2_out_scaled);
            break;

        case AP_MOTORS_HELI_DUAL_MODE_TRANSVERSE:
            mix_transverse(pitch_out, roll_out, yaw_out, collective_out_scaled, collective2_out_scaled);
            break;

        case AP_MOTORS_HELI_DUAL_MODE_INTERMESHING:
            mix_intermeshing(pitch_out, roll_out, yaw_out, collective_out_scaled, collective2_out_scaled);
            break;

    }

}

void AP_MotorsHeli_Dual::output_to_motors()
{
    if (!initialised_ok()) {
        return;
    }

    // Write swashplate outputs
    _swashplate1.output();
    _swashplate2.output();

    update_motor_control(get_rotor_control_state());

}

// servo_test - move servos through full range of movement
void AP_MotorsHeli_Dual::servo_test()
{
    // this test cycle is equivalent to that of AP_MotorsHeli_Single, but excluding
    // mixing of yaw, as that physical movement is represented by pitch and roll

    _servo_test_cycle_time += _dt;

    if ((_servo_test_cycle_time >= 0.0f && _servo_test_cycle_time < 0.5f)||                                   // Tilt swash back
        (_servo_test_cycle_time >= 6.0f && _servo_test_cycle_time < 6.5f)){
        _pitch_test += 2.0 * _dt;
        _oscillate_angle += 8 * M_PI * _dt;
    } else if ((_servo_test_cycle_time >= 0.5f && _servo_test_cycle_time < 4.5f)||                            // Roll swash around
               (_servo_test_cycle_time >= 6.5f && _servo_test_cycle_time < 10.5f)){
        _oscillate_angle += 0.5 * M_PI * _dt;
        _roll_test = sinf(_oscillate_angle);
        _pitch_test = cosf(_oscillate_angle);
    } else if ((_servo_test_cycle_time >= 4.5f && _servo_test_cycle_time < 5.0f)||                            // Return swash to level
               (_servo_test_cycle_time >= 10.5f && _servo_test_cycle_time < 11.0f)){
        _pitch_test -= 2.0 * _dt;
        _oscillate_angle += 8 * M_PI * _dt;
    } else if (_servo_test_cycle_time >= 5.0f && _servo_test_cycle_time < 6.0f){                              // Raise swash to top
        _collective_test +=  _dt;
        _oscillate_angle += 2 * M_PI * _dt;
    } else if (_servo_test_cycle_time >= 11.0f && _servo_test_cycle_time < 12.0f){                            // Lower swash to bottom
        _collective_test -=  _dt;
        _oscillate_angle += 2 * M_PI * _dt;
    } else {                                                                                                  // reset cycle
        _servo_test_cycle_time = 0.0f;
        _oscillate_angle = 0.0f;
        _collective_test = 0.0f;
        _roll_test = 0.0f;
        _pitch_test = 0.0f;
        // decrement servo test cycle counter at the end of the cycle
        if (_servo_test_cycle_counter > 0){
            _servo_test_cycle_counter--;
        }
    }

    // over-ride servo commands to move servos through defined ranges

    _throttle_filter.reset(constrain_float(_collective_test, 0.0f, 1.0f));
    _roll_in = constrain_float(_roll_test, -1.0f, 1.0f);
    _pitch_in = constrain_float(_pitch_test, -1.0f, 1.0f);
}

// Run arming checks
bool AP_MotorsHeli_Dual::arming_checks(size_t buflen, char *buffer) const
{
    // run base class checks
    if (!AP_MotorsHeli::arming_checks(buflen, buffer)) {
        return false;
    }

    // returns false if Phase Angle is outside of range for H3 swashplate 1
    if (_swashplate1.get_swash_type() == SWASHPLATE_TYPE_H3 && (_swashplate1.get_phase_angle() > 30 || _swashplate1.get_phase_angle() < -30)){
        hal.util->snprintf(buffer, buflen, "H_SW1_H3_PHANG out of range");
        return false;
    }

    // returns false if Phase Angle is outside of range for H3 swashplate 2
    if (_swashplate2.get_swash_type() == SWASHPLATE_TYPE_H3 && (_swashplate2.get_phase_angle() > 30 || _swashplate2.get_phase_angle() < -30)){
        hal.util->snprintf(buffer, buflen, "H_SW2_H3_PHANG out of range");
        return false;
    }

    return true;
}