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Add <damper> actuator shortcut and related mjGAIN_AFFINE.

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**Rationale**

A general `mjGAIN_AFFINE` actuator adds the term `force = (c + kp * length + kv * velocity) * ctrl`. The damper shortcut restricts it to `kv * velocity * ctrl` and sets the `ctrllimited` attribute to true.

**API**

```xml
<actuator>
  <damper ctrlrange="0 1" kv="1"/>
</actuator>
```

* Required attributes: `ctrlrange` (>=0)
* Optional attributes: `kv` (>=0)

PiperOrigin-RevId: 455366866
Change-Id: I88773abbeccabb6442f215c9fc05e205df63f692
This commit is contained in:
Alessio Quaglino
2022-06-16 06:20:49 -07:00
committed by Copybara-Service
parent e0b6ba4a13
commit 307cf692e5
14 changed files with 283 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files
test/engine/engine_derivative_test.cc
+7 -1
View File
@@ -71,13 +71,16 @@ static const char* const kTumblingThinObjectPath =
"engine/testdata/derivative/tumbling_thin_object.xml";
static const char* const kDampedActuatorsPath =
"engine/testdata/derivative/damped_actuators.xml";
static const char* const kDamperActuatorsPath =
"engine/testdata/damper.xml";
// compare analytic and finite-difference d_smooth/d_qvel
TEST_F(DerivativeTest, SmoothDvel) {
// run test on all models
for (const char* local_path : {kEnergyConservingPendulumPath,
kTumblingThinObjectPath,
kDampedActuatorsPath}) {
kDampedActuatorsPath,
kDamperActuatorsPath}) {
const std::string xml_path = GetTestDataFilePath(local_path);
mjModel* model = mj_loadXML(xml_path.c_str(), nullptr, nullptr, 0);
mjData* data = mj_makeData(model);
@@ -88,6 +91,9 @@ TEST_F(DerivativeTest, SmoothDvel) {
// take 100 steps so we have some velocities, then call forward
mj_resetData(model, data);
if (model->nu) {
data->ctrl[0]=0.1;
}
for (int i=0; i<100; i++) {
mj_step(model, data);
}
test/engine/engine_forward_test.cc
+37
View File
@@ -89,6 +89,43 @@ TEST_F(ForwardTest, ActLimited) {
mj_deleteModel(model);
}
// --------------------------- damping actuator --------------------------------
TEST_F(ForwardTest, DamperDampens) {
static constexpr char xml[] = R"(
<mujoco>
<worldbody>
<body>
<geom size="1"/>
<joint name="jnt" type="slide" axis="1 0 0" range="-10 10"/>
</body>
</worldbody>
<actuator>
<motor joint="jnt"/>
<damper joint="jnt" kv="1000" ctrlrange="0 100"/>
</actuator>
</mujoco>
)";
mjModel* model = LoadModelFromString(xml);
mjData* data = mj_makeData(model);
// move the joint
data->ctrl[0] = 100.0;
data->ctrl[1] = 0.0;
for (int i=0; i<100; i++)
mj_step(model, data);
// stop the joint with damping
data->ctrl[0] = 0.0;
data->ctrl[1] = 100.0;
for (int i=0; i<1000; i++)
mj_step(model, data);
EXPECT_LE(data->qvel[0], std::numeric_limits<double>::epsilon());
mj_deleteData(data);
mj_deleteModel(model);
}
// --------------------------- implicit integrator -----------------------------
using ImplicitIntegratorTest = MujocoTest;
test/engine/testdata/damper.xml
Vendored
+15
View File
@@ -0,0 +1,15 @@
<mujoco>
<worldbody>
<geom type="plane" size="1 1 .01"/>
<light pos="0 0 2"/>
<body pos="0 0 .3">
<joint name="hinge" axis="0 1 0"/>
<geom type="capsule" size=".01" fromto="0 0 0 .2 0 0"/>
<geom size=".03" pos=".2 0 0"/>
</body>
</worldbody>
<actuator>
<damper name="damper" joint="hinge" kv="10" ctrlrange="0 1"/>
</actuator>
</mujoco>