The dcmotor input block is any subset of the canonical list [pos, vel,
ff, voltage], selected with input="pos vel ff voltage" and recorded as
mjtCtrlInput bits in actuator_ctrlspec like pid. Tokens are required in
canonical order: the attribute denotes a set, the block always packs
canonically, and accepting permutations invites reading the string as a
layout choice. The mode flag in gainprm[8] is retired (reserved,
written 0).
Controller gains are now in torque space, as for pid: the controller
commands tau = kp*(q*-l) + kd*(v*-ldot) + ki*x_I + tau_ff over the
present inputs (absent setpoints frozen at zero) and converts to drive
voltage V = R/K * tau + K*ldot. The second term compensates back-EMF,
as the current loop of a real torque-mode driver does (torque commands
are current commands): commanded torque is delivered exactly until a
limit binds, and the torque-speed envelope emerges from the Vmax clamp.
The map uses the nameplate R: thermal resistance growth is not
compensated, so a hot motor under-delivers by R/R(T). A stateless
setpoint dcmotor now matches <pid> exactly, for any K and R; the old
back-EMF droop remains available as the physical behavior of the raw
voltage path. Voltage-space datasheet gains convert by K/R. Controller
inputs require a positive motor constant (the map divides by K), and
controller gains require a controller input.
ff and voltage are distinct inputs, different in kind: ff is a torque
feedforward added to the controller output, uniform with pid's ff
(feedforward in the actuator's output space), while voltage is the raw
terminal voltage of the physical device, injected downstream of the
controller and its Vmax clamp, unclamped (ctrlrange bounds it if
desired). input="voltage" is the default: the plain voltage-commanded
motor, whose behavior is unchanged by this commit. The integrator
always accumulates position error; the old velocity mode's integral
term, ki*(int(u)dt - theta), which tracked the integral of the velocity
command, is retired without replacement, keeping ki mode-independent --
commanded integrated velocity belongs to an integrator activation
state, not to controller gains. slewmax rate-limits the first controller
input -- position setpoint (rad/s), velocity setpoint (rad/s^2) or torque
feedforward (N*m/s), each a real driver feature (reference ramping,
ramped-velocity and ramped-torque input modes); the raw voltage input
is never rate-limited and slewmax requires a controller input.
input="none" selects the empty signature: the actuator owns no controls
at all (nu = 0 is now legal with actuators present) and is purely
passive -- LuGre friction, cogging and back-EMF braking as passive
joint forces. This exists because auxiliary dynamic states (the LuGre
bristle) attach to actuators, not joints. The terminal voltage is
identically zero, i.e. a shorted motor (dynamic braking); motorconst=0
decouples the electrical branch. mjINPUT_NONE is a distinct enum value
because ctrlspec = 0 means "unset, use the type default". History and
delay require an input; the controller voltage override and input read
in mj_fwdActuation are gated on a nonempty block.
The analytic velocity derivative of the controller becomes
dV/dw = -kd*R/K + K, whose second term cancels the back-EMF bias
exactly: the net damping of an unclipped torque-mode motor is -kd, and
of a voltage-mode or passive motor -K^2/R. Viewers label inputs via
mj_actuatorInputName: pos, vel, ff, voltage.
The dcmotor LaTeX design doc is updated accordingly: torque-space
units, the tau->V map and its saturation-generated envelope, the
input-block pipeline figure, and a Passive Operation section.
PiperOrigin-RevId: 965795351
Change-Id: Ibc308ca21bd6bad014e77f950ee08feaad449b73
Replaces the box-box collider's manifold generation and post-filtering with a
single structured implementation, and deletes the accumulated repair logic it
obsoletes. Net 319 lines out of the engine.
Algorithm:
- The separating-axis test keeps the closed-form support evaluation and chooses
the axis of maximum separation among the 15 candidates by plain argmax.
Edge-cross axes whose cross product has norm below rounding are skipped: in
the nearly-parallel regime their direction is cancellation noise, previously
the source of arbitrary-normal contacts with box-scale spurious depth. A
winning edge axis within eight degrees of the best face axis is replaced by
that face unless it is better by five percent (ODE's classic fudge): resting
stacks otherwise flip between the edge and face contact codes by rounding
noise from step to step, thrashing the solver warm start until the stack
explodes. The substitution runs after the search rather than filtering during
it, so a worse non-aliasing edge cannot steal the contact the substitution
meant to give to the face.
- Face contacts clip the incident face against the reference face's side planes
(Sutherland-Hodgman). Depth is measured along the reference normal only,
never as a Euclidean distance between unrelated points. Contact position is
midway between the surfaces along the normal, so its distance to either box
is bounded by half the contact depth. Every surviving vertex of the clipped
polygon becomes a contact, so the manifold is the actual contact patch, at
most eight points as before.
- Edge contacts use the closest-point pair between the two supporting edge
segments. A near-zero axis component makes the support-corner sign ambiguous;
both signs are enumerated and the closest witness pair wins.
- Margin is an acceptance band throughout: SAT early-out and clip acceptance.
- The rounding thresholds are stated per precision. The separation tests are
the ones that cost correctness: comparing exactly against the margin reports
a pair overlapping by less than the rounding error of its own support
evaluation as separated, and the boxes pass through each other. Over 239k
overlapping pairs that is eight misses under mjUSESINGLE and none in double;
the collider this replaces misses the same eight. Slack proportional to the
summed half-sizes leaves five, which overlap by 7e-9 to 3e-8 of their own
scale, below single-precision epsilon, where the boxes are not distinguishable
from touching. Erring toward contact is the safe direction: the driver already
excludes a contact whose distance reaches the margin.
Deleted: the conditional acceptance cascade keyed on how many points earlier
generators emitted, the u/v clamping that fabricated contacts from out-of-range
projections, the outside-box removal filter and its missing-fallback hole,
exact-floating-point deduplication, and the edge-path depth clamp. The
structure makes those bug classes unrepresentable rather than filtered: depth
is a projection by construction. Every reported depth is the exact support
overlap along the contact's own normal, verified over 246k overlapping poses to
within two ulps; the face preference costs direction, not depth, deviating from
the minimum-translation axis by at most 8.1 degrees and 5.3% of its depth.
The previous implementation is preserved verbatim as mjc_BoxBoxLegacy in
test/engine/boxbox_legacy.c, a static library that only the box-box tests link,
so the claims above are measured rather than asserted. It needs no private
engine symbols. Three tests compare against it:
- NearAlignedManifoldIsExact sweeps the relative angle of a resting pair across
the regime where the edge-cross axes degenerate into noise, pinning the full
clipped polygon and a contact normal equal to the face normal exactly, where
the previous collider drifts off it.
- AlignedTowerStands settles a twenty-box tower, which comes to rest four
million times quieter than under the previous collider, which never settles
and eventually topples.
- ShallowOverlapSurvivesRounding pins a pair overlapping by 7e-8 of its scale,
reported as separated under mjUSESINGLE without slack on the separation tests.
On stacks of plates across aspect ratios from 4:1 to 25:1, five layouts each,
the collider settles into a tight band of 1e-4 to 3e-4 while the previous one
intermittently blows up to as much as 2.6e-2.
engine_collision_box_fuzz_test.cc cross-validates randomized poses against
GJK/EPA on identical box meshes and against a spherical-Fibonacci support
sweep, with hard gates per sample: no phantom penetration, no missed contact at
zero margin, no contact deeper than the true depth, contacts within half their
own depth of both boxes, and one normal per manifold. Both invocations run in
about a second.
EdgeContactAtDepthBound's tolerance widens to the five percent design band; the
three-orders-of-magnitude depth bug it pins is still caught, the deviation
being 0.13 percent of the depth.
The 100-box pile benchmark steps about 7% faster with 1.6% fewer contacts.
PiperOrigin-RevId: 965114952
Change-Id: Ie98cdcce8d1aed3ff2da938cb29703fd9c241258
https://youtu.be/17XpwnqyCXs
New transmission type mjTRN_SO3: a relative orientation, targeting a ball
joint or a site+refsite pair. It is the first transmission with more than
one force output: its length is the norm of the expmap vector of the
relative rotation and its moment axes are the 3 rows of the
relative rotational Jacobian, without projecting onto per-actuator gears.
New force law mjGAIN_SO3/mjBIAS_SO3: a geodesic PD servo, force =
kp * log(q_current^-1 * q_target) - kv * velocity, exact for arbitrary axis
combinations with a unique equilibrium at every commanded orientation.
Error, moment rows and velocity all live in the child frame (joint or
site): the right-difference error is the gradient of the geodesic
potential in that frame. The parent-frame (left) error is not: driving
child-frame torques with it pumps energy at large angles, settling into
steady-spinning limit cycles (the SO3LargeAngleConvergence test). The
integrator variant stores the 3D orientation setpoint in act (actnum = 3,
re-anchored to a bounded representative at integration time). Exposed in
MJCF as <orientation joint=|site=+refsite= kp kv|dampratio>, or via
<general gaintype="so3" biastype="so3">.
The setpoint input has two charts: an expmap target (3 controls, default)
or a quaternion target (4 controls) -- <orientation input="quat">, the
first actuator with different input and output widths. The signature is
recorded in a new per-actuator field actuator_ctrlspec (mjtCtrlChart),
whose meaning is scoped by the gain type the way gain/bias parameters are;
ctrlnum is derived from it at compile time and remains the layout
authority. An explicit field rather than width inference or a prm slot:
width-as-chart cannot express same-width signatures (upcoming servo input
subsets), and prm slots are the input_mode pattern this stack retires.
The force law normalizes the commanded quaternion, making it scale- and
antipodally-invariant. The all-zero ctrl still maps to the identity via
mju_normalize4, but it is a degenerate point (a nudge of any component
commands a half-turn), so quat inputs reset to the identity quaternion:
new mj_resetCtrl sets neutral ctrl values (zero, except qw = 1), called
by mj_resetData and the viewers' Clear All. The quat chart is
restricted to dyntype 'none': integrating a quaternion setpoint linearly
is not meaningful on the manifold. New mjsActuator.ctrlspec field carries
the signature through the spec and XML round-trip.
Actuator sensors (actuatorpos/vel/frc) now report one value per force
output; dim = 3 on an SO3 actuator.
As the first actuator with nu != nactuator, this commit also makes the
viewers multi-input aware: the control sliders in simulate and studio,
which indexed per-actuator arrays by control index (out of bounds on
this model class), are generated per control and labeled with the
actuator name plus an input suffix ("orient/qw"), via the new
introspection helper mj_actuatorInputName -- the single source of truth
for input names, extended by each new multi-input type (quaternion
components are w-first: qw, qx, qy, qz). Slider ranges now honor a
defined ctrlrange even when ctrllimited is false: range is the UI hint,
limited is the clamp -- wrapped and expmap setpoints are unbounded but
still want finite sliders, while quat components are truly bounded.
The rotational demo model is orientation.xml under
test/engine/testdata/actuation/, upgraded to a three-way contrast:
per-axis wrapped servos vs an expmap-commanded vs a quat-commanded
orientation actuator, on identical checker-textured boxes. It is loaded
by the mixed-axis contrast and input-name tests, and doubles as the
viewer test model (slider groups of 3 independent, 3 grouped, 4 grouped).
PiperOrigin-RevId: 951607063
Change-Id: If235dba8e2f2ca72672e7c62531a27e967c6a373
https://www.youtube.com/watch?v=PdSdrqhSiZA
The new geom attribute surfacevel (6 numbers: linear and angular velocity in the geom's local frame, angular about the geom frame origin) specifies the velocity of the geom's surface material relative to the geom frame. The relative surface velocity of the two geoms is added to the tangential contact rows of efc_vel in mj_referenceConstraint, so friction drives touching bodies toward the motion of the surface: objects on a conveyor are transported at belt speed, turntables impart omega x r with torsional spin-up for condim >= 4, and surface velocities compose with each other and with body motion. The component along the contact normal is projected out: probe experiments showed that velocity-space emission chatters mass-independently and ingestion merely deepens penetration; normal-direction effects belong to force-space features.
surfacevel is interpreted in the geom frame as authored: for mesh geoms, whose compiled frame absorbs the mesh centering and principal-axes transform, the compiler re-expresses the authored value in the compiled frame.
No special interaction with sleeping: objects being transported do not fall asleep because they are moving; objects at rest on an active surface may sleep like any other resting object.
Includes showcase models (model/surfacevel/): a luggage carousel whose ring is a spinning square-profile supertorus fed by a cascade of belts with matched spinning end rollers, bags dropping in and circulating indefinitely; and a treadmill with a passive humanoid.
PiperOrigin-RevId: 948647785
Change-Id: I0c6559a91cc7ece1237eb8ac2e51986e7342d962
- Remove `lugre:viscous`, should now be added directly to actuator `damping`. Trying to do this for the user was incompatible with default inheritance (compounding instead of overriding).
- Move voltage limiting from the `saturation` to the `controller` attribute.
- Fix indexing issues in default inheritance.
PiperOrigin-RevId: 897087642
Change-Id: I5388c2633e15c7e223992e7eb5d6a28db75a6438
Notes:
- Currently always uses dense math, even for sparse models. This should be easy to change in the future.
- Does not support geom wrapping. This is possible but harder, requires derivatives of mju_wrap.
PiperOrigin-RevId: 740378741
Change-Id: Id39ef2c4bfbb7ee11ec33c97d7d83140441cdab2
Yuval Tassa