Datasets:

introvoyz041
/

mujoco

	// 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.

	// Tests for the PID controller plugin

	#include <string>
	#include <string_view>
	#include <vector>

	#include <gmock/gmock.h>
	#include <gtest/gtest.h>
	#include <absl/cleanup/cleanup.h>
	#include <absl/strings/str_replace.h>
	#include <absl/strings/string_view.h>
	#include <mujoco/mujoco.h>
	#include "test/fixture.h"

	namespace mujoco {
	namespace {

	using PidTest = PluginTest;
	using ::testing::DoubleNear;
	using ::testing::HasSubstr;
	using ::testing::IsNull;
	using ::testing::NotNull;

	TEST_F(PidTest, PGain) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1"><config key="kp" value="4.0"/></instance>
	</plugin>
	</extension>

	<option gravity="0 0 0"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" />
	<position joint="j2" kp="4.0" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	EXPECT_EQ(m->plugin_statenum[0], 0)
	<< "Plugin should have no state variables";
	EXPECT_EQ(m->actuator_actnum[0], 0)
	<< "Plugin should have no activation variables";

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// apply the same ctrl to both actuators and see if the same qpos results
	d->ctrl[0] = 1.0;
	d->ctrl[1] = 1.0;

	mj_step(m, d);

	EXPECT_EQ(d->actuator_force[0], d->actuator_force[1]);
	EXPECT_EQ(d->qfrc_actuator[0], d->qfrc_actuator[1]);
	EXPECT_EQ(d->qpos[0], d->qpos[1]);
	}

	TEST_F(PidTest, PGainWithFilterExact) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1"><config key="kp" value="4.0"/></instance>
	</plugin>
	</extension>

	<option gravity="0 0 0"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" actdim="1"
	dyntype="filterexact" dynprm="0.1" actearly="true"/>
	<general joint="j2" gainprm="4.0 0 0" biastype="affine" biasprm="0 -4.0 0"
	dyntype="filterexact" dynprm="0.1" actearly="true"/>
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	EXPECT_EQ(m->plugin_statenum[0], 0)
	<< "Plugin should have no state variables";
	EXPECT_EQ(m->actuator_actnum[0], 1)
	<< "Plugin should have one activation variable";

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// apply the same ctrl to both actuators and see if the same qpos results
	d->ctrl[0] = 1.0;
	d->ctrl[1] = 1.0;

	for (int i = 0; i < 2; i++) {
	mj_step(m, d);

	EXPECT_EQ(d->actuator_force[0], d->actuator_force[1]);
	EXPECT_EQ(d->qfrc_actuator[0], d->qfrc_actuator[1]);
	EXPECT_EQ(d->qpos[0], d->qpos[1]);
	}
	}

	TEST_F(PidTest, SlewMaxRate) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 0" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" actdim="1" />
	<position joint="j2" kp="4.0" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// having a slew rate means that there should be one extra state variable
	// for the plugin.
	EXPECT_EQ(m->actuator_actnum[0], 1);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// going from ctrl=0.0 to ctrl=1.0 immediately should be equivalent to slowly
	// incrementing the setpoint
	d->ctrl[0] = d->ctrl[1] = 0.0;
	mj_step(m, d);

	mjtNum max_slew_rate = 0.75;
	for (int i = 0; i < 2; i++) {
	d->ctrl[0] = 1.0;
	d->ctrl[1] = d->time * max_slew_rate;
	mj_step(m, d);

	EXPECT_EQ(d->actuator_force[0], d->actuator_force[1])
	<< "actuator_force mismatch at step " << i;
	EXPECT_EQ(d->qfrc_actuator[0], d->qfrc_actuator[1])
	<< "qfrc_actuator mismatch at step " << i;
	EXPECT_EQ(d->qpos[0], d->qpos[1]) << "qpos mismatch at step " << i;
	}
	}

	TEST_F(PidTest, IntegratedVelocitySlewMaxRate) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	<instance name="pid2">
	<config key="kp" value="4.0"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 0" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" actdim="1"/>
	<!-- make an integrated velocity controller using the PID plugin -->
	<plugin joint="j2" plugin="mujoco.pid" instance="pid2"
	dyntype="integrator" dynprm="1 0 0" actearly="true" actdim="1"/>
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// having a slew rate means that there should be one extra state variable
	// for the plugin.
	ASSERT_EQ(m->actuator_actnum[0], 1);
	// The integrated-velocity controller should have one activation variable too.
	ASSERT_EQ(m->actuator_actnum[1], 1);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// going from ctrl=0.0 to ctrl=1.0 immediately should be equivalent to using
	// an integrated-velocity controller, with actearly = true
	d->ctrl[0] = d->ctrl[1] = 0.0;
	mj_step(m, d);

	mjtNum max_slew_rate = 0.75;
	for (int i = 0; i < 2; i++) {
	d->ctrl[0] = 1.0;
	d->ctrl[1] = max_slew_rate;
	mj_step(m, d);

	EXPECT_EQ(d->act[0], d->act[1])
	<< "act mismatch at step " << i;
	EXPECT_EQ(d->actuator_force[0], d->actuator_force[1])
	<< "actuator_force mismatch at step " << i;
	EXPECT_EQ(d->qfrc_actuator[0], d->qfrc_actuator[1])
	<< "qfrc_actuator mismatch at step " << i;
	EXPECT_EQ(d->qpos[0], d->qpos[1]) << "qpos mismatch at step " << i;
	}
	}

	TEST_F(PidTest, SlewMaxRateUsesFirstCtrl) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 0" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" actdim="1"/>
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// When starting with ctrl = 1.0, there shouldn't be a slew rate restriction
	d->ctrl[0] = 1.0;
	mj_forward(m, d);
	EXPECT_EQ(d->actuator_force[0], 4.0);
	}

	TEST_F(PidTest, ITerm) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid2">
	<config key="kp" value="40.0"/>
	<config key="ki" value="40"/>
	<config key="kd" value="4"/>
	</instance>
	<instance name="pid3">
	<config key="kp" value="40.0"/>
	<config key="ki" value="40"/>
	<config key="kd" value="4"/>
	<config key="imax" value="5"/>
	</instance>
	<!-- intentionally put the plugin instances out of order, to test
	any accidentaly dependency on the plugin definition order matching
	the actuator order.
	-->
	<instance name="pid1">
	<config key="kp" value="40.0"/>
	<config key="kd" value="4"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 -10" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	<body pos="0.08 0 0" >
	<joint name="j3" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" />
	<plugin joint="j2" plugin="mujoco.pid" instance="pid2" actdim="1" />
	<plugin joint="j3" plugin="mujoco.pid" instance="pid3" actdim="1" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// only the actuators with an I term should have state.
	EXPECT_EQ(m->actuator_actnum[0], 0);
	EXPECT_EQ(m->actuator_actnum[1], 1);
	EXPECT_EQ(m->actuator_actnum[2], 1);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// when applying a constant 1.0 control for a while:
	// - the PD controller should settle to 1.0 - m*g / kp
	// - the unclamped PID controller should reach 1.0
	// - the clamped PID controller should reach 1.0 - (m*g - imax) / kp
	d->ctrl[0] = d->ctrl[1] = d->ctrl[2] = 1.0;
	for (int i = 0; i < 10000; i++) {
	mj_step(m, d);
	}

	EXPECT_THAT(d->qpos[0], DoubleNear(1.0 - 10 / 40.0, 1e-5));
	EXPECT_THAT(d->qpos[1], DoubleNear(1.0, 1e-5));
	EXPECT_THAT(d->qpos[2], DoubleNear(1.0 - (10 - 0.125 * 40.0) / 40.0, 1e-5));
	}

	TEST_F(PidTest, FiniteDifferencing) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid">
	<config key="ki" value="40"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<worldbody>
	<body><joint name="j"/><geom size="0.01"/></body>
	</worldbody>

	<actuator>
	<plugin joint="j" plugin="mujoco.pid" instance="pid" actdim="2" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// actuators with an I term and max slew rate should have 2 activation
	// variables.
	ASSERT_EQ(m->actuator_actnum[0], 2);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	d->ctrl[0] = 1.0;
	mj_step(m, d);
	EXPECT_NE(d->act[0], 0);
	mjtNum state_before_finite_differencing = d->act[0];

	std::vector<mjtNum> A((2m->nv+m->na) (2*m->nv+m->na), 0);
	std::vector<mjtNum> B((2m->nv+m->na) m->nu, 0);
	std::vector<mjtNum> C((m->nsensordata) * (2*m->nv+m->na), 0);
	std::vector<mjtNum> D((m->nsensordata) * m->nu, 0);
	mjd_transitionFD(m, d, /eps=/1e-3, /flg_centered=/true, A.data(),
	B.data(), C.data(), D.data());

	EXPECT_EQ(d->act[0], state_before_finite_differencing)
	<< "mjd_transitionFD should not change actuator plugin state.";
	}

	TEST_F(PidTest, CtrlClamp) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<compiler autolimits="true"/>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid">
	<config key="kp" value="40.0"/>
	<config key="ki" value="40"/>
	<config key="kd" value="4"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 0" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid"
	ctrlrange="0.25 0.75" actdim="1" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// when applying a constant 1.0 control for a while, control should be clamped
	// to 0.75, and the body should reach that point.
	d->ctrl[0] = 1.0;
	for (int i = 0; i < 10000; i++) {
	mj_step(m, d);
	}
	EXPECT_THAT(d->qpos[0], DoubleNear(0.75, 1e-5));

	// when applying 0, it should be clamped to 0.25
	d->ctrl[0] = 0.0;
	for (int i = 0; i < 10000; i++) {
	mj_step(m, d);
	}
	EXPECT_THAT(d->qpos[0], DoubleNear(0.25, 1e-5));
	}

	TEST_F(PidTest, CopyData) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="40.0"/>
	<config key="kd" value="4"/>
	</instance>
	<instance name="pid2">
	<config key="kp" value="40.0"/>
	<config key="ki" value="40"/>
	<config key="kd" value="4"/>
	<config key="slewmax" value="3.14" />
	<config key="imax" value="1"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 -10" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide" axis="0 0 1" />
	<geom size="0.01" mass="1"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" />
	<plugin joint="j2" plugin="mujoco.pid" instance="pid2" actdim="2"/>
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	mjData* d1 = mj_makeData(m);
	absl::Cleanup d1_deleter = [d1] { mj_deleteData(d1); };

	d1->ctrl[0] = d1->ctrl[1] = -1.0;

	for (int i = 0; i < 3; i++) {
	mj_step(m, d1);
	}
	mjData* d2 = mj_copyData(nullptr, m, d1);
	absl::Cleanup d2_deleter = [d2] { mj_deleteData(d2); };

	mj_step(m, d1);
	mj_step(m, d2);

	EXPECT_EQ(d1->qpos[0], d2->qpos[0]);
	EXPECT_EQ(d1->qpos[1], d2->qpos[1]);
	}

	TEST_F(PidTest, MultipleActuatorsSamePlugin) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<option gravity="0 0 0" timestep="0.001"/>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	<body pos="0.04 0 0" >
	<joint name="j2" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid" actdim="1" />
	<plugin joint="j2" plugin="mujoco.pid" instance="pid" actdim="1" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// having a slew rate means that there should be one extra state variable
	// for the plugin.
	EXPECT_EQ(m->actuator_actnum[0], 1);
	EXPECT_EQ(m->actuator_actnum[1], 1);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	// Set different ctrls for the two actuators, and check that they're
	// independent.
	d->ctrl[0] = 1.0;
	d->ctrl[1] = -1.0;

	for (int i = 0; i < 2; i++) {
	mj_step(m, d);

	EXPECT_EQ(d->actuator_force[0], -d->actuator_force[1])
	<< "actuator_force mismatch at step " << i;
	EXPECT_EQ(d->qfrc_actuator[0], -d->qfrc_actuator[1])
	<< "qfrc_actuator mismatch at step " << i;
	EXPECT_EQ(d->qpos[0], -d->qpos[1]) << "qpos mismatch at step " << i;
	}
	}

	TEST_F(PidTest, InvalidClamp) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="ki" value="40"/>
	<!-- imax should be nonnegative -->
	<config key="imax" value="-0.01"/>
	</instance>
	</plugin>
	</extension>

	<worldbody>
	<body><joint name="j1" /><geom size="0.01" /></body>
	</worldbody>

	<actuator><plugin joint="j1" plugin="mujoco.pid" instance="pid1" /></actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	EXPECT_THAT(m, IsNull());

	EXPECT_THAT(std::string_view(error), HasSubstr("plugin"));
	EXPECT_THAT(std::string_view(error), HasSubstr("imax"));
	}

	TEST_F(PidTest, InvalidSlew) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="40"/>
	<!-- slewmax must be nonnegative -->
	<config key="slewmax" value="-0.1"/>
	</instance>
	</plugin>
	</extension>

	<worldbody>
	<body><joint name="j" /><geom size="0.01" /></body>
	</worldbody>

	<actuator>
	<plugin joint="j" plugin="mujoco.pid" instance="pid1" />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, IsNull());

	EXPECT_THAT(std::string_view(error), HasSubstr("plugin"));
	EXPECT_THAT(std::string_view(error), HasSubstr("slewmax"));
	}

	TEST_F(PidTest, WrongActdim) {
	// XML where PLACEHOLDER is going to be replaced with various things
	constexpr absl::string_view kBaseXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" PLACEHOLDER />
	</actuator>
	</mujoco>
	)";

	char error[1024] = {0};
	{
	std::string no_actdim =
	absl::StrReplaceAll(kBaseXml, {{"PLACEHOLDER", ""}});
	mjModel* m = LoadModelFromString(no_actdim, error, sizeof(error));
	EXPECT_THAT(m, IsNull());
	EXPECT_THAT(std::string_view(error), HasSubstr("actdim=\"1\""));
	}

	{
	std::string big_actdim =
	absl::StrReplaceAll(kBaseXml, {{"PLACEHOLDER", "actdim=\"2\""}});
	mjModel* m = LoadModelFromString(big_actdim, error, sizeof(error));
	EXPECT_THAT(m, IsNull());
	EXPECT_THAT(std::string_view(error), HasSubstr("actdim=\"1\""));
	}

	{
	std::string dyntype_integrator = absl::StrReplaceAll(
	kBaseXml, {{"PLACEHOLDER", "dyntype=\"integrator\" actdim=\"1\""}});
	mjModel* m = LoadModelFromString(dyntype_integrator, error, sizeof(error));
	EXPECT_THAT(m, IsNull());
	EXPECT_THAT(std::string_view(error), HasSubstr("actdim=\"2\""));
	}
	}

	// Regression test: loading models with PID plugin and keyframes used to crash.
	TEST_F(PidTest, Keyframe) {
	constexpr absl::string_view kModelXml = R"(
	<mujoco>
	<extension>
	<plugin plugin="mujoco.pid">
	<instance name="pid1">
	<config key="kp" value="4.0"/>
	<config key="slewmax" value="0.75"/>
	</instance>
	</plugin>
	</extension>

	<worldbody>
	<body>
	<joint name="j1" type="slide"/>
	<geom size="0.01"/>
	</body>
	</worldbody>

	<actuator>
	<plugin joint="j1" plugin="mujoco.pid" instance="pid1" actdim="1" />
	</actuator>
	<keyframe>
	<key name="home" qpos="0" act="1" />
	</keyframe>
	</mujoco>
	)";

	char error[1024] = {0};
	mjModel* m = LoadModelFromString(kModelXml, error, sizeof(error));
	ASSERT_THAT(m, NotNull()) << error;
	absl::Cleanup m_deleter = [m] { mj_deleteModel(m); };

	// having a slew rate means that there should be one extra state variable
	// for the plugin.
	EXPECT_EQ(m->actuator_actnum[0], 1);
	EXPECT_EQ(m->na, 1);
	ASSERT_EQ(m->nkey, 1);
	EXPECT_EQ(m->key_act[0], 1.0);

	mjData* d = mj_makeData(m);
	absl::Cleanup d_deleter = [d] { mj_deleteData(d); };

	mj_resetDataKeyframe(m, d, 0);
	EXPECT_EQ(d->act[0], 1.0);
	}
	} // namespace
	} // namespace mujoco