mirror of https://github.com/ArduPilot/ardupilot
AP_WheelRateControl: lib to control wheel rate with encoders
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Randy Mackay
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912dd0c4cc
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#include <AP_WheelEncoder/AP_WheelRateControl.h>
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extern const AP_HAL::HAL& hal;
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const AP_Param::GroupInfo AP_WheelRateControl::var_info[] = {
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// @Param: _ENABLE
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// @DisplayName: Wheel rate control enable/disable
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// @Description: Enable or disable wheel rate control
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// @Values: 0:Disabled,1:Enabled
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// @User: Standard
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AP_GROUPINFO_FLAGS("_ENABLE", 1, AP_WheelRateControl, _enabled, 0, AP_PARAM_FLAG_ENABLE),
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// @Param: _RATE_MAX
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// @DisplayName: Wheel max rotation rate
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// @Description: Wheel max rotation rate
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// @Units: rad/s
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// @Range: 0 200
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// @User: Standard
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AP_GROUPINFO("_RATE_MAX", 2, AP_WheelRateControl, _rate_max, AP_WHEEL_RATE_MAX_DEFAULT),
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// @Param: _RATE_FF
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// @DisplayName: Wheel rate control feed forward gain
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// @Description: Wheel rate control feed forward gain. Desired rate (in radians/sec) is multiplied by this constant and output to output (in the range -1 to +1)
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// @Range: 0.100 2.000
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// @User: Standard
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// @Param: _RATE_P
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// @DisplayName: Wheel rate control P gain
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// @Description: Wheel rate control P gain. Converts rate error (in radians/sec) to output (in the range -1 to +1)
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// @Range: 0.100 2.000
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// @User: Standard
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// @Param: _RATE_I
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// @DisplayName: Wheel rate control I gain
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// @Description: Wheel rate control I gain. Corrects long term error between the desired rate (in rad/s) and actual
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// @Range: 0.000 2.000
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// @User: Standard
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// @Param: _RATE_IMAX
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// @DisplayName: Wheel rate control I gain maximum
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// @Description: Wheel rate control I gain maximum. Constrains the output (range -1 to +1) that the I term will generate
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// @Range: 0.000 1.000
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// @User: Standard
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// @Param: _RATE_D
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// @DisplayName: Wheel rate control D gain
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// @Description: Wheel rate control D gain. Compensates for short-term change in desired rate vs actual
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// @Range: 0.000 0.400
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// @User: Standard
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// @Param: _RATE_FILT
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// @DisplayName: Wheel rate control filter frequency
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// @Description: Wheel rate control input filter. Lower values reduce noise but add delay.
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// @Range: 1.000 100.000
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// @Units: Hz
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// @User: Standard
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AP_SUBGROUPINFO(_rate_pid0, "_RATE_", 3, AP_WheelRateControl, AC_PID),
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// @Param: 2_RATE_FF
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// @DisplayName: Wheel rate control feed forward gain
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// @Description: Wheel rate control feed forward gain. Desired rate (in radians/sec) is multiplied by this constant and output to output (in the range -1 to +1)
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// @Range: 0.100 2.000
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// @User: Standard
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// @Param: 2_RATE_P
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// @DisplayName: Wheel rate control P gain
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// @Description: Wheel rate control P gain. Converts rate error (in radians/sec) to output (in the range -1 to +1)
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// @Range: 0.100 2.000
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// @User: Standard
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// @Param: 2_RATE_I
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// @DisplayName: Wheel rate control I gain
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// @Description: Wheel rate control I gain. Corrects long term error between the desired rate (in rad/s) and actual
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// @Range: 0.000 2.000
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// @User: Standard
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// @Param: 2_RATE_IMAX
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// @DisplayName: Wheel rate control I gain maximum
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// @Description: Wheel rate control I gain maximum. Constrains the output (range -1 to +1) that the I term will generate
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// @Range: 0.000 1.000
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// @User: Standard
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// @Param: 2_RATE_D
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// @DisplayName: Wheel rate control D gain
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// @Description: Wheel rate control D gain. Compensates for short-term change in desired rate vs actual
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// @Range: 0.000 0.400
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// @User: Standard
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// @Param: 2_RATE_FILT
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// @DisplayName: Wheel rate control filter frequency
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// @Description: Wheel rate control input filter. Lower values reduce noise but add delay.
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// @Range: 1.000 100.000
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// @Units: Hz
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// @User: Standard
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AP_SUBGROUPINFO(_rate_pid1, "2_RATE_", 4, AP_WheelRateControl, AC_PID),
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AP_GROUPEND
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};
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AP_WheelRateControl::AP_WheelRateControl(const AP_WheelEncoder &wheel_encoder_ref) :
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_wheel_encoder(wheel_encoder_ref)
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{
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AP_Param::setup_object_defaults(this, var_info);
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}
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// returns true if a wheel encoder and rate control PID are available for this instance
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bool AP_WheelRateControl::enabled(uint8_t instance)
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{
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// sanity check instance
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if ((instance > 1) || (_enabled == 0)) {
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return false;
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}
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// wheel encoder enabled
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return _wheel_encoder.enabled(instance);
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}
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// get throttle output in the range -100 to +100 given a desired rate expressed as a percentage of the rate_max (-100 to +100)
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// instance can be 0 or 1
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float AP_WheelRateControl::get_rate_controlled_throttle(uint8_t instance, float desired_rate_pct, float dt)
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{
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if (!enabled(instance)) {
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return 0;
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}
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// determine which PID instance to use
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AC_PID& rate_pid = (instance == 0) ? _rate_pid0 : _rate_pid1;
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// set PID's dt
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rate_pid.set_dt(dt);
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// check for timeout
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uint32_t now = AP_HAL::millis();
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if (now - _last_update_ms > AP_WHEEL_RATE_CONTROL_TIMEOUT_MS) {
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rate_pid.reset_filter();
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rate_pid.reset_I();
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_limit[instance].lower = false;
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_limit[instance].upper = false;
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}
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_last_update_ms = now;
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// convert desired rate as a percentage to radians/sec
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float desired_rate = desired_rate_pct / 100.0f * get_rate_max_rads();
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// get actual rate from wheeel encoder
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float actual_rate = _wheel_encoder.get_rate(instance);
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// calculate rate error and pass to pid controller
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float rate_error = desired_rate - actual_rate;
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rate_pid.set_input_filter_all(rate_error);
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// store desired and actual for logging purposes
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rate_pid.set_desired_rate(desired_rate);
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rate_pid.set_actual_rate(actual_rate);
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// get ff
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float ff = rate_pid.get_ff(desired_rate);
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// get p
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float p = rate_pid.get_p();
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// get i unless we hit limit on last iteration
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float i = rate_pid.get_integrator();
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if (((is_negative(rate_error) && !_limit[instance].lower) || (is_positive(rate_error) && !_limit[instance].upper))) {
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i = rate_pid.get_i();
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}
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// get d
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float d = rate_pid.get_d();
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// constrain and set limit flags
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float output = ff + p + i + d;
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// set limits for next iteration
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_limit[instance].upper = output >= 100.0f;
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_limit[instance].lower = output <= -100.0f;
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return output;
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}
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// get pid objects for reporting
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AC_PID& AP_WheelRateControl::get_pid(uint8_t instance)
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{
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if (instance == 0) {
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return _rate_pid0;
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} else {
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return _rate_pid0;
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}
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}
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@ -0,0 +1,73 @@
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/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <AP_Common/AP_Common.h>
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#include <AP_Math/AP_Math.h>
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#include <AP_Param/AP_Param.h>
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#include <AC_PID/AC_PID.h>
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#include <AP_WheelEncoder/AP_WheelEncoder.h>
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// wheel rate control defaults
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#define AP_WHEEL_RATE_MAX_DEFAULT 12.0f // maximum wheel rotation rate in rad/sec (about 115rpm, 687deg/sec)
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#define AP_WHEEL_RATE_CONTROL_FF 8.00f
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#define AP_WHEEL_RATE_CONTROL_P 2.00f
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#define AP_WHEEL_RATE_CONTROL_I 2.00f
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#define AP_WHEEL_RATE_CONTROL_IMAX 1.00f
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#define AP_WHEEL_RATE_CONTROL_D 0.01f
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#define AP_WHEEL_RATE_CONTROL_FILT 0.00f
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#define AP_WHEEL_RATE_CONTROL_DT 0.02f
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#define AP_WHEEL_RATE_CONTROL_TIMEOUT_MS 200
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class AP_WheelRateControl {
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public:
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AP_WheelRateControl(const AP_WheelEncoder &wheel_encoder_ref);
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// returns true if a wheel encoder and rate control PID are available for this instance
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bool enabled(uint8_t instance);
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// get throttle output in the range -100 to +100 given a desired rate expressed as a percentage of the rate_max (-100 to +100)
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// instance can be 0 or 1
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float get_rate_controlled_throttle(uint8_t instance, float desired_rate_pct, float dt);
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// get rate maximum in radians/sec
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float get_rate_max_rads() const { return MAX(_rate_max, 0.0f); }
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// get pid objects for reporting
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AC_PID& get_pid(uint8_t instance);
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static const struct AP_Param::GroupInfo var_info[];
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private:
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// parameters
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AP_Int8 _enabled; // top level enable/disable control
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AP_Float _rate_max; // wheel maximum rotation rate in rad/s
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AC_PID _rate_pid0 = AC_PID(AP_WHEEL_RATE_CONTROL_P, AP_WHEEL_RATE_CONTROL_I, AP_WHEEL_RATE_CONTROL_D, AP_WHEEL_RATE_CONTROL_IMAX, AP_WHEEL_RATE_CONTROL_FILT, AP_WHEEL_RATE_CONTROL_DT, AP_WHEEL_RATE_CONTROL_FF);
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AC_PID _rate_pid1 = AC_PID(AP_WHEEL_RATE_CONTROL_P, AP_WHEEL_RATE_CONTROL_I, AP_WHEEL_RATE_CONTROL_D, AP_WHEEL_RATE_CONTROL_IMAX, AP_WHEEL_RATE_CONTROL_FILT, AP_WHEEL_RATE_CONTROL_DT, AP_WHEEL_RATE_CONTROL_FF);
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// limit flags
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struct AP_MotorsUGV_limit {
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bool lower; // reached this instance's lower limit on last iteration
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bool upper; // reached this instance's upper limit on last iteration
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} _limit[2];
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// internal variables
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const AP_WheelEncoder& _wheel_encoder; // pointer to accompanying wheel encoder
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uint32_t _last_update_ms; // system time of last call to get_rate_controlled_throttle
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};
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