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Add the pid actuator: setpoint inputs, integral action, slew rate limiting.

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<pid kp kv|dampratio [ki imax] [slewmax]> is a PID controller with real position and velocity setpoint inputs on a single force output, plus an optional feedforward input. With a zero velocity setpoint it reproduces <position> bit-exactly; the input signature is any subset of [pos, vel, ff], selected with input="..." and recorded as mjtCtrlInput bits in
actuator_ctrlspec; absent setpoint inputs are fixed at zero, so the control vector contains no inert entries.

kp and kv are single-sourced in the affine bias parameters (biasprm[1,2]) with no gainprm mirror: every consumer of the position-servo shape
(dampratio conversion, inheritrange, qDeriv) reads one location, which is what makes the bit-exact <position> parity possible. Controller state uses dyntype 'pid' with slot-gated activations in the order [slew, integral], following the dcmotor slot idiom: slewmax (dynprm[1]) rate limits the effective position setpoint through an activation holding it;
ki (gainprm[0]) integrates the position error -- wrapped on rotational transmissions -- with anti-windup clamping of the integrand at imax (dynprm[0]). Both features require the pos input. Servo input unpacking is shared with the dcmotor controller (unpackServoInputs); per-input ranges are exposed as posrange/velrange/ffrange.

This subsumes the functionality of the mujoco.pid plugin with proper activation state: correct under all integrators, visible to keyframes, act sensors and reset. Migration: kp/ki/kd map to kp/ki/kv, plugin imax is in force units (divide by ki), slewmax carries over; the single ctrl becomes input="pos".

PiperOrigin-RevId: 957588898
Change-Id: Id2786836ca6e76f58e5b5cc8323fc23be0a53784
This commit is contained in:
Yuval Tassa
2026-08-01 04:28:10 -07:00
committed by Copybara-Service
parent 7bc1aa9b05
commit 279df98cd0
33 changed files with 1504 additions and 62 deletions
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src/xml/xml_native_writer.cc
+14 -1
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@@ -899,7 +899,20 @@ void mjXWriter::OneActuator(XMLElement* elem, const mjCActuator* actuator, mjCDe
// non-plugins: write actuator parameters
else {
WriteAttrKey(elem, "gaintype", gain_map, gain_sz, actuator->gaintype, def->Actuator().gaintype);
WriteAttrKey(elem, "input", input_map, input_sz, actuator->ctrlspec, def->Actuator().ctrlspec);
if (actuator->gaintype == mjGAIN_SO3) {
WriteAttrKey(elem, "input", inputchart_map, inputchart_sz, actuator->ctrlspec,
def->Actuator().ctrlspec);
} else if (actuator->ctrlspec != def->Actuator().ctrlspec) {
std::string tokens;
for (int k=0; k < inputbit_sz; k++) {
if (actuator->ctrlspec & inputbit_map[k].value) {
tokens += std::string(tokens.empty() ? "" : " ") + inputbit_map[k].key;
}
}
WriteAttrTxt(elem, "input", tokens);
}
WriteAttr(elem, "velrange", 2, actuator->velrange, def->Actuator().velrange);
WriteAttr(elem, "ffrange", 2, actuator->ffrange, def->Actuator().ffrange);
WriteAttrKey(elem, "biastype", bias_map, bias_sz, actuator->biastype, def->Actuator().biastype);
WriteAttr(elem, "gainprm", mjNGAIN, actuator->gainprm, def->Actuator().gainprm, true);
WriteAttr(elem, "biasprm", mjNBIAS, actuator->biasprm, def->Actuator().biasprm, true);