| // Copyright 2023 DeepMind Technologies Limited | |
| // | |
| // 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. | |
| 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 | |