Motor Control Week 1 Flashcards
Why is movement easy to us
Just because we can do it doesn’t mean it is easy. Complicated high level control strategies are used by our brain, even when we are thought Lesley doing simple motor tasks
What is fitts law?
The law predicts the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target.
What problems to engineers face when trying to grab and Apple
Need to
- localisation and planning to reach the apple
- execution and control
- adaptation.
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What is space?
Set (of points) with some added structures
What two repensentatives spaces are used in robotics?
Internal and external
- external ( end effector space, task space, operational space)
-internal ( configuration space, joint angle space, body space)
What are coordinate systems
Set of numbers that uniquely determine a point in space.
A single space can have multiple coordinates
Also called coordinate frame/reference frame
What are the three types of coordinate systems
1) Cartesian coordinates system ( x, y,z)
2) cylindrical coordinate system ( angle, distance, height)
3) spherical coordinate system (two different angles and heights)
What are the two types of origins of coordinate systems?
1) egocentric (coordinates systems attached to our body
2) allocentric ( coordinates systems attached to external world or object)
What are coordinate transformations?
the transformation between different coordinate systems
What is forward and inverse kinematics (coordinate transformations)
inverse kinematics (from furthest point to myself) - configuration space - forward kinematics (myself to furthest point) - end effector space
adding forces and torques to kinematics
linear vs angular kinematics (distance vs angle)
linear vs angular kinetics (forces vs torques
dynamics : forwards and inverse dynamics
inverse dynamics - kinetics - forward dynamics - kinematics
newtons second law
newtons second law defines the relationship between kinematics and dynamics.
F=Ma
f=force
M=Inertia
a= accerleration
What is control
manipulating something to do something
what are the two types of control strategies?
1) plan in advance
2) policies (case by case action)
what are the pros and cons of planning?
pros
- very clear about what to do , so you don’t waste time checking and asking around.
cons
- if you make any mistake the consequences of your mistake is unrecoverable
- if there is any unexpected event
- if you want to for from different stations you need a brand-new plan
What are the pros and cons of policies?
pros
- flexible
-robust
-general
cons
- you have to ask every time to fo your action
- people give you random answers can you really trust the,
- slow at giving answers
Which control is feedforward and feedback
feedforward (open loop)= plan
feedback (closed loop) = policies
feedforward controller pros and cons
pros
- movement can be controlled without external info
-fast
cons
- error made
-no flexibility
-high cost in planning
policies pros and cons
pros
- flexible
-robust
-general
cons
- time consuming
-unstable
- unstable when feedbacks are delayed
what is variability
even when the same movement is repeated, controller behaviors under uncertainties result in movement patterns
What is sensory information needed for?
localisation and planning
intrinsic - in your body, muscle spindles, mechanoreceptors
extrinsic - outside your body, vascular info and auditory info
what are spinal reflexes used for
spinal reflexes are mostly involuntary : sensory inputs cause motor outputs directly without intervention of higher brain centers
however voluntary movements require higherlevels cortical control
