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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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python/mujoco/specs_test.py
+9
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@@ -1596,6 +1596,15 @@ class SpecsTest(absltest.TestCase):
self.assertEqual(actuator.biastype, mujoco.mjtBias.mjBIAS_SO3)
self.assertEqual(actuator.dyntype, mujoco.mjtDyn.mjDYN_NONE)
actuator.set_to_pid(kp=2.0, kv=3.0, ki=0.5, imax=1.5, slewmax=4.0)
self.assertEqual(actuator.biasprm[1], -2)
self.assertEqual(actuator.biasprm[2], -3)
self.assertEqual(actuator.gainprm[0], 0.5)
self.assertEqual(actuator.dynprm[0], 1.5)
self.assertEqual(actuator.dynprm[1], 4.0)
self.assertEqual(actuator.gaintype, mujoco.mjtGain.mjGAIN_PID)
self.assertEqual(actuator.dyntype, mujoco.mjtDyn.mjDYN_PID)
actuator.set_to_velocity(kv=5.0)
self.assertEqual(actuator.gainprm[0], 5)
self.assertEqual(actuator.biasprm[2], -5)