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//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef MUJOCO_PLUGIN_ACTUATOR_PID_H_
#define MUJOCO_PLUGIN_ACTUATOR_PID_H_
#include <memory>
#include <optional>
#include <vector>
#include <mujoco/mjdata.h>
#include <mujoco/mjmodel.h>
#include <mujoco/mjtnum.h>
namespace mujoco::plugin::actuator {
struct PidConfig {
double p_gain = 0.0;
double i_gain = 0.0;
double d_gain = 0.0;
// Maximum value of the error integral.
// NOTE: In the XML definition, the clamp values are specified as limits on
// the *force* value, so are scaled by i_gain.
std::optional<double> i_max;
// Maximum speed at which the setpoint can change.
std::optional<double> slew_max;
// Reads plugin attributes to construct PID configuration.
static PidConfig FromModel(const mjModel* m, int instance);
};
// An actuator plugin which implements configurable PID control.
class Pid {
public:
// Returns an instance of Pid. The result can be null in case of
// misconfiguration.
static std::unique_ptr<Pid> Create(const mjModel* m, int instance);
// Returns the number of state variables for the plugin instance
static int StateSize(const mjModel* m, int instance);
// Resets the C++ Pid instance's state.
// plugin_state is a C array pointer into mjData->plugin_state, with a size
// equal to the value returned from StateSize.
void Reset(mjtNum* plugin_state);
// Computes the rate of change for activation variables
void ActDot(const mjModel* m, mjData* d, int instance) const;
// Idempotent computation which updates d->actuator_force and the internal
// state of the class. Called after ActDot.
void Compute(const mjModel* m, mjData* d, int instance);
// Updates plugin state.
void Advance(const mjModel* m, mjData* d, int instance) const;
// Adds the PID plugin to the global registry of MuJoCo plugins.
static void RegisterPlugin();
private:
Pid(PidConfig config, std::vector<int> actuators);
// Returns the expected number of activation variables for the instance.
static int ActDim(const mjModel* m, int instance, int actuator_id);
struct State {
mjtNum previous_ctrl = 0;
// if using slew rate limits, mjData.act will contain an activation variable
// with the last ctrl value. If `false`, that value should be ignored,
// because it hasn't been set yet.
bool previous_ctrl_exists = false;
mjtNum integral = 0;
};
// Reads data from d->act and returns it as a State struct.
State GetState(const mjModel* m, mjData* d, int actuator_idx) const;
// Returns the PID setpoint, which is normally d->ctrl, but can be d->act for
// actuators with dyntype != none.
mjtNum GetCtrl(const mjModel* m, const mjData* d, int actuator_idx,
const State& state, bool actearly) const;
PidConfig config_;
// set of actuator IDs controlled by this plugin instance.
std::vector<int> actuators_;
};
} // namespace mujoco::plugin::actuator
#endif // MUJOCO_PLUGIN_ACTUATOR_PID_H_
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