MechanismState

Index

The MechanismState type

RigidBodyDynamics.MechanismState — Type.
immutable MechanismState{X<:Number, M<:Number, C<:Number}

A MechanismState stores state information for an entire Mechanism. It contains the joint configuration and velocity vectors $q$ and $v$, as well as cache variables that depend on $q$ and $v$ and are aimed at preventing double work.

Type parameters:

  • X: the scalar type of the $q$ and $v$ vectors.

  • M: the scalar type of the Mechanism

  • C: the scalar type of the cache variables (== promote_type(X, M))

source

Functions

RigidBodyDynamics.configuration — Method.
configuration(state, joint)

Return the part of the configuration vector $q$ associated with joint.

source
RigidBodyDynamics.configuration — Method.
configuration(state)

Return the configuration vector $q$.

Note that this returns a reference to the underlying data in state. The user is responsible for calling setdirty! after modifying this vector to ensure that dependent cache variables are invalidated.

source
RigidBodyDynamics.global_coordinates! — Method.
global_coordinates!(state, q0, ϕ)

Convert local coordinates $phi$ centered around $q_0$ to (global) configuration vector $q$.

source
RigidBodyDynamics.local_coordinates! — Method.
local_coordinates!(state, ϕ, ϕd, q0)

Compute local coordinates $phi$ centered around (global) configuration vector $q_0$, as well as their time derivatives $\dot{\phi}$.

source
RigidBodyDynamics.num_positions — Method.
num_positions(state)

Return the length of the joint configuration vector $q$.

source
RigidBodyDynamics.num_velocities — Method.
num_velocities(state)

Return the length of the joint velocity vector $v$.

source
RigidBodyDynamics.rand_configuration! — Method.
rand_configuration!(state)

Randomize the configuration vector $q$. The distribution depends on the particular joint types present in the associated Mechanism. The resulting $q$ is guaranteed to be on the Mechanism's configuration manifold. Invalidates cache variables.

source
RigidBodyDynamics.rand_velocity! — Method.
rand_velocity!(state)

Randomize the velocity vector $v$. Invalidates cache variables.

source
RigidBodyDynamics.relative_transform — Method.
relative_transform(state, from, to)

Return the homogeneous transform from from to to.

source
RigidBodyDynamics.relative_twist — Method.
relative_twist(state, bodyFrame, baseFrame)

Return the twist of bodyFrame with respect to baseFrame, expressed in the Mechanism's root frame.

source
RigidBodyDynamics.relative_twist — Method.
relative_twist(state, body, base)

Return the twist of body with respect to base, expressed in the Mechanism's root frame.

source
RigidBodyDynamics.set_configuration! — Method.
set_configuration!(state, q)

Set the configuration vector $q$. Invalidates cache variables.

source
RigidBodyDynamics.set_configuration! — Method.
set_configuration!(state, joint, q)

Set the part of the configuration vector associated with joint. Invalidates cache variables.

source
RigidBodyDynamics.set_velocity! — Method.
set_velocity!(state, v)

Set the velocity vector $v$. Invalidates cache variables.

source
RigidBodyDynamics.set_velocity! — Method.
set_velocity!(state, joint, v)

Set the part of the velocity vector associated with joint. Invalidates cache variables.

source
RigidBodyDynamics.setdirty! — Method.
setdirty!(state)

Invalidate all cache variables.

source
RigidBodyDynamics.velocity — Method.
velocity(state, joint)

Return the part of the velocity vector $v$ associated with joint.

source
RigidBodyDynamics.velocity — Method.
velocity(state)

Return the velocity vector $v$.

Note that this function returns a read-write reference to a field in state. The user is responsible for calling setdirty! after modifying this vector to ensure that dependent cache variables are invalidated.

source
RigidBodyDynamics.zero! — Method.
zero!(state)

Zero both the configuration and velocity. Invalidates cache variables.

See zero_configuration!, zero_velocity!.

source
RigidBodyDynamics.zero_configuration! — Method.
zero_configuration!(state)

'Zero' the configuration vector $q$. Invalidates cache variables.

Note that when the Mechanism contains e.g. quaternion-parameterized joints, $q$ may not actually be set to all zeros; the quaternion part of the configuration vector would be set to identity. The contract is that each of the joint transforms should be an identity transform.

source
RigidBodyDynamics.zero_velocity! — Method.
zero_velocity!(state)

Zero the velocity vector $v$. Invalidates cache variables.

source
Base.Random.rand! — Method.
rand!(state)

Randomize both the configuration and velocity. Invalidates cache variables.

source
RigidBodyDynamics.non_tree_joints — Method.
non_tree_joints(state)

Return the Joints that are not part of the underlying Mechanism's spanning tree as an iterable collection.

source