Download 12-ControlStrantegies

Motor Control Engineering View
Topics:
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1- Muscle and Spinal Cord Models
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2- Classic Control/Control Variables
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3- Model Based Strategies
Classic Control
(Modeling Eye Movement)
Stark, Lawrence W. 1968.
Neurological Control Systems;
Studies in Bioengineering.
New York: Plenum Press.
Control Variables
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123456-
Force !?
Position !?
Velocity !?
Stiffness !?
Viscosity !?
Impedance !?
Stein, R.C. (1982)
Behavioral and Brain Sciences
What Muscle Variable(s) Does the
Nervous System Control in Limb
Movements?
Stiffness Control
Muscle Stiffness
F = k ( X – X0) :)‫رابطه يك فنر (عضله‬
Stiffness Control (cont.)

K = F/X
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K >> 1 => Force Control
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K << 1 => Position Control
Stiffness Control (cont.)
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1- Feldman & Bizzi (EPH),
1966,1979,1986
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2- Houk (Stiffness and Reflex), 1979
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3- Hasan, 1986
How CNS May Changes
Joint Stiffness?
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1- Muscle active characteristic
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2- Muscle passive characteristic
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3- α-γ co-activation & spinal reflex loop
(muscle spindle)
4- Co-contraction
Stiffness Control Diagram
Disturbance
Td
Receptors
Delay
Brain Model
d
Trajectory
Selector


Feedforward
Controller
Joint Movement
Spinal Torque
Circuits
Joint-Load
and
Dynamics

Muscles
Load Effect
βv = Θf - Td/σ
Torque
2
Td

Angle
1
i=1

f=2
Stiffness Control Diagram (cont.)
CNS
d
Optimizer
Program

Inverse
Dynamic
Controller
Disturbance
Td
G (s)
Delay

f
v
Delay


G(s)

orque)
( Angle )
Impedance Definition:
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Winters et al. (1988):
“the automatic capability of the system
to resist an applied load before
voluntary intervention takes place”
Impedance Control
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1- Hoffer (1982). Central Control and
Reflex Regulation of Mechanical
Impedance: The Basis for a Unified
Motor-Control Scheme. Behavioral and
Brain Sciences
Impedance Control (cont.)
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2- Stein, R. C., (1982). What Muscle
Variable(s) Does the Nervous System
Control in Limb Movements?
Behavioral and Brain Sciences
Impedance Control (cont.)
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3-Hogan, N., (1984a). Adaptive Control of
Mechanical Impedance by Coactivation of
Antagonist Muscles. IEEE Trans. on Automatic
Control,
Hogan, N., (1985a). Impedance Control: An
Approach to Manipulation: Part I-Theory.
Journal of Dynamic Systems, Measurement,
and Control,
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Hogan, N., (1985c). The Mechanics of MultiJoint Posture and Movement Control.
Biological Cybernetic, 52, 315-331.
Muscle 2-D Characteristic
Joint Impedance
orque)

( Angle )
 ( Torque )
b
 (Angular Velocity )
Is Joint Impedance ShortTerm Predictor?
Joint Impedance (cont.)
Reference
Output
PD
Plant
Control Signal
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Smith, A. M. (1996) ,
Does the Cerebellum Learn Strategies
for the Optimal Time-Varing Control of
Joint Stiffness? Behavioral and Brain
Sciences