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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
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src/xml/xml_native_reader.cc
+36 -2
View File
@@ -41,7 +41,7 @@ using tinyxml2::XMLElement;
//---------------------------------- MJCF schema ---------------------------------------------------
static const int nMJCF = 160;
static const int nMJCF = 162;
static const char* MJCF[nMJCF][mjXATTRNUM] = {
{"mujoco", "!", "1", "model"},
{"<"},
@@ -134,6 +134,9 @@ static const char* MJCF[nMJCF][mjXATTRNUM] = {
"ctrlrange", "forcerange", "actrange",
"gear", "cranklength", "user", "group",
"kp"},
{"damper", "?", "8", "forcelimited", "ctrlrange", "forcerange",
"gear", "cranklength", "user", "group",
"kv"},
{"cylinder", "?", "12", "ctrllimited", "forcelimited", "ctrlrange", "forcerange",
"gear", "cranklength", "user", "group",
"timeconst", "area", "diameter", "bias"},
@@ -283,6 +286,11 @@ static const char* MJCF[nMJCF][mjXATTRNUM] = {
"gear", "cranklength", "user",
"joint", "jointinparent", "tendon", "slidersite", "cranksite", "site",
"kp"},
{"damper", "*", "17", "name", "class", "group",
"forcelimited", "ctrlrange", "forcerange",
"lengthrange", "gear", "cranklength", "user",
"joint", "jointinparent", "tendon", "slidersite", "cranksite", "site",
"kv"},
{"cylinder", "*", "21", "name", "class", "group",
"ctrllimited", "forcelimited", "ctrlrange", "forcerange",
"lengthrange", "gear", "cranklength", "user",
@@ -521,9 +529,10 @@ const mjMap dyn_map[dyn_sz] = {
// gain type
const int gain_sz = 3;
const int gain_sz = 4;
const mjMap gain_map[gain_sz] = {
{"fixed", mjGAIN_FIXED},
{"affine", mjGAIN_AFFINE},
{"muscle", mjGAIN_MUSCLE},
{"user", mjGAIN_USER}
};
@@ -1490,6 +1499,30 @@ void mjXReader::OneActuator(XMLElement* elem, mjCActuator* pact) {
}
}
// damper
else if (type=="damper") {
// clear bias
mjuu_zerovec(pact->gainprm, mjNGAIN);
// explicit attributes
ReadAttr(elem, "kv", 1, pact->gainprm+2, text);
if (pact->gainprm[2]<0)
throw mjXError(elem, "damping coefficient cannot be negative");
pact->gainprm[2] = -pact->gainprm[2];
// Require nonnegative range
ReadAttr(elem, "ctrlrange", 2, pact->ctrlrange, text);
if (pact->ctrlrange[0]<0 || pact->ctrlrange[1]<0) {
throw mjXError(elem, "control range cannot be negative");
}
// implied parameters
pact->ctrllimited = true;
pact->dyntype = mjDYN_NONE;
pact->gaintype = mjGAIN_AFFINE;
pact->biastype = mjBIAS_NONE;
}
// cylinder
else if (type=="cylinder") {
// explicit attributes
@@ -1795,6 +1828,7 @@ void mjXReader::Default(XMLElement* section, int parentid) {
name=="motor" ||
name=="position" ||
name=="velocity" ||
name=="damper" ||
name=="intvelocity" ||
name=="cylinder" ||
name=="muscle") {