Lie Group Formulation for Robot Mechanics Terry Taewoong Um [email protected] Adaptive Systems Laboratory Electrical and Computer Engineering University of Waterloo
Jul 18, 2015
Lie Group Formulation
for Robot Mechanics
Terry Taewoong Um
Adaptive Systems LaboratoryElectrical and Computer Engineering
University of Waterloo
These slides are made based
on Junnggon Kim’s note
http://www.cs.cmu.edu/~junggon/tools/liegroupdynamics.pdf
made by Terry. T. Um ([email protected])
Dynamics of a Rigid Body
made by Terry. T. Um ([email protected])
Rigid Body Motion
ab : cord. {B} w.r.t cord. {A}
• se(3) : Lie algebra of SE(3)
4x4
4x4
skew symmetric matrix
• Adjoint mapping
• SO(3) & SE(3)
4x4
made by Terry. T. Um ([email protected])
or6x6
or
dse(3) mapping
Generalized Velocity & Force
• Coordinate Transformation Rules
4x4
• Generalized Velocity & Force
made by Terry. T. Um ([email protected])
or6x6
𝝎 / 𝒗 : angular / linear velocity of the {body} attached to the body relativerelative to the {space} but expressed @{body}
𝑭 : a moment and force action on the body viewed @{body}
Let {A}, {B} be two different coord. frames attached to the same body but diff. pos.
(recall )
𝑭 ∈ dse(3)
• Notation @{body} : w.r.t the frame attached to the (moving) body@{space} : w.r.t. the frame attached to the (fixed) reference frame
Generalized Inertial & Momentum
• Coordinate Transformation Rules
• Kinematic Energy
made by Terry. T. Um ([email protected])
Let {A}, {B} be two different coord. frames attached to the same body but diff. pos.
: generalized inertia @{body}
6x6
3x3 inertia matrix @{body}
= 0 if the origin islocated on the CoM
if the origin @CoM
: generalized momentum @{body}
like
Time Derivative and Force
• Time derivative of se(3) & dse(3)
• Time derivative of a 3-dim vector
made by Terry. T. Um ([email protected])
• Generalized Force
component-wisetime derivative
whole derivative component-wisetime derivative
Dynamics of Open Chain Systems
made by Terry. T. Um ([email protected])
Hybrid Dynamics
• Hybrid Dynamics : Mixture of Forward & Inverse Dynamics
made by Terry. T. Um ([email protected])
u : inverse dynamics, i.e. v : forward dynamics, i.e.
thus,
• Notation
: inertial frame (stationary)
: the frame of the ith body
: the frame of the parent of the ith body
Recursive Inverse Dynamics
• Generalized Velocity of the ith frame
made by Terry. T. Um ([email protected])
relative velocity w.r.t. its parent
: Jacobin of the joint i connecting with it parents
• To build the dynamics equations for each body, 𝑽 is required
: 𝑉 is requiraedForce of a rigid body :
Recursive Inverse Dynamics
• Time derivative of the generalized velocity, 𝑽
made by Terry. T. Um ([email protected])
recall
• Force of the i th body, 𝑭𝒊
propagated forcesexternal force acting
on the ith bodyrecall
reaction
Recursive Inverse Dynamics
• Recursive Inverse Dynamics Algorithm
made by Terry. T. Um ([email protected])
Recursive Inverse Dynamics
made by Terry. T. Um ([email protected])
Recursive Inverse Dynamics (Comparison)
made by Terry. T. Um ([email protected])
Recursive Inverse Dynamics (Comparison)
made by Terry. T. Um ([email protected])