Final Exam Flashcards
What are problems of inverse kinematics
Joint Angles
what are problems with inverse dynamics
Joint Torques
Bernstin Problem:
Two approaches:
- The central controller finds a unique solution each time a problem emerges
- Central controller facilitates groups of equally acceptable solutions rather than unique solutions
The first one says that there is only one choice
The second says that Instead of having to settle on one decision, there are several choices as long as it is in an acceptable range
This allows selection for a unique solution to a problem:
Optimization Approaches:
•A common approach to the problem of motor redundancy is to apply optimization criteria
Cost Function:
Cost function:
•Particular function of a system’s performance the controller tries to keep optimized, commonly at a minimum value
•Imagine a single joint movement being performed as quickly as possible
•Movement time is a cost function to be minimized
Abundancy:(principle of abundance)
Abundancy:(principle of abundance)
- Instead of redundancy, there is abundancy (multiple possibilities)
- the degrees of freedom at teach level of the movement system do not pose computational problems
- instead of searching for unique solutions, the controller can facilitate similar solutions that can solve the task.
_________•a task-specific organization of elements, while each element within a structural unit is itself a structural unit at a different level of the analysis
•Structural units: a task specific organization of elements, while each element within a structural unit is itself a structural unit at a different level of the analysis
•__________: purposes of structural units
•Synergies: purposes of structural units
•____________: extrinsic patterns reflecting a synergy under particular external conditions
•Behaviors: extrinsic patterns reflecting a synergy under particular external conditions
- __________: based on a structural unit that consists of a neural network uniting different extremities.
- _________of the arms or legs is based on a structural unit comprising individual joint rotations.
- Locomotion: based on a structural unit that consists of a neural network uniting different extremities.
- Motion of the arms or legs is based on a structural unit comprising individual joint rotations.
- Each joint rotation is based on a structural unit involving muscle actions as elements.
- Each muscle is a structural unit of its motor units.
- Each joint rotation is based on a structural unit involving muscle actions as elements.
- Each muscle is a structural unit of its motor units.
________:an inverted in the field of gravity
Posture :an inverted in the field of gravity
_________________: maintenance of body alignment and spatial orientation in order to put the body in a position to enable effective movement
Postural control: maintenance of body alignment and spatial orientation in order to put the body in a position to enable effective movement.
____________: Maintaining stability, upright stability, resisting disturbances to stability.
Postural Control: Maintaining stability, upright stability, resisting disturbances to stability.
Sources of Problems:
- High center of mass/center of gravity
- Multiple Joints
- Small support area (1 square foot)
- Stability: a position that is resistant to disturbance or returns to its normal state After disturbance
Sources of Problems:
- High center of mass/center of gravity
- Multiple Joints
- Small support area (1 square foot)
- Stability: a position that is resistant to disturbance or returns to its normal state After disturbance
What is the center of gravity for Males & Females?
- Female’s CG is ~ 55% of standing height.
- Male’s CG is ~ 57% of standing height.
in quiet standing, the _______ can be considered to be almost directly over the center of pressure.
in quiet standing, the Center of gravity can be considered to be almost directly over the center of pressure.
Sway increases under these conditions:
The following will increase sway:
- Closed eyes (one needs a reference frame)
- standing on a narrow support
- age, disorder
Sway decreases under these conditions:
Decreases sway
- light finger touch (to virtually any part of the body)
- Holding an object connected to the external world
_________ must remain within the base of support in order to maintain equilibrium.
Center of gravity must remain within the base of support in order to maintain equilibrium.
________ base of support = less mobility
Larger/wider base of support = less mobility
___________: migration of the reference point, with respect to which equilibrium is instantly maintained; likely a reflection of a central search process Supraspinal process
Rambling: migration of the reference point, with respect to which equilibrium is instantly maintained; likely a reflection of a central search process Supraspinal process
_________\_: likely a reflection of the Mechanical properties of the effectors and reflex loops Subspinal process
Trembling: likely a reflection of the Mechanical properties of the effectors and reflex loops Subspinal process
•They are innervated by the peripheral ends of bipolar sensory neurons in the ampullary nerve.
Vestibular hair cells
The ___________ is covered by a gelatinous,diaphragm-like mass called the cupula.
The ampullary crest is covered by a gelatinous,diaphragm-like mass called the cupula.
____________: sensitive to angular acceleration of the head
- The fluid in the semicircular canals move when the head rotates
- This fluid acts on the cupula and displaces the hair cells, which generate APs
Semicircular canals: sensitive to angular acceleration of the head
- The fluid in the semicircular canals move when the head rotates
- This fluid acts on the cupula and displaces the hair cells, which generate APs
___________: sensitive to linear acceleration of the head
- In the utricle, a portion of the floor is thickened and contains hair receptors
- This zone is called the macula It is covered with a gelatinous substance containing crystals of calcium carbonate (______)
- When you tilt your head or accelerate in a certain direction, the otoliths deform the gelatinous surface, which bend the hair cells (generate APs)
Otoliths: sensitive to linear acceleration of the head
- In the utricle, a portion of the floor is thickened and contains hair receptors
- This zone is called the macula It is covered with a gelatinous substance containing crystals of calcium carbonate ( Otoliths )
- When you tilt your head or accelerate in a certain direction, the otoliths deform the gelatinous surface, which bend the hair cells (generate APs)
- Innervated by the ______ nerve via Scarpa’s (vestibular) ganglion. Neurons here are bipolar.
- Vestibular nuclei occupy a large part of the medulla
- Innervated by the eighth nerve via Scarpa’s (vestibular) ganglion. Neurons here are bipolar.
- vestibular nuclei occupy a large part of the medulla
The sensation of moving forward will have a ______ sway of the body?
The sensation of moving forward will have a backward sway of the body?
What Is Necessary
to Maintain Posture?
What Is Necessary
to Maintain Posture?
- Adequate perception of a reference point or reference vertical
- Timely generation of appropriate muscle torques
- Control of posture under external and internal perturbations
Many differences of ____________ _________, some caused by our own movements
- Many Voluntary movements are associated with changes in the activity of postural muscles, even before the movement begins
- These ________ ________ ________ (APAs) are to minimize perturbations to vertical posture
- Many differences in postural perturbations, some caused by our own movements
- Many Voluntary movements are associated with changes in the activity of postural muscles, even before the movement begins
- These anticipatory postural adjustments (APAs) are to minimize perturbations to vertical posture
What mechanisms help maintain Posture?
- APA’s <0 sec (Based on a prediction of a perturbation)
- Muscle elasticity 0sec
- monosynaptic reflex 30ms
- polysynaptic reflex 50ms
- preprogramed reaction 70ms
- voluntary action 150ms (LATE)
A fast arm movement by a standing person is a source of a _____________ perturbation because of the joint coupling.
A fast arm movement by a standing person is a source of a strong postural perturbation because of the joint coupling.
A fast shoulder flexion creates reactive torques (Tr) that try to tilt the body Backward.
- ________ are generated prior to a perturbation.
- It helps if the perturbation is predictable.
- The perturbation is typically associated with an action by the person.
- _________ produce forces/torques acting against the expected perturbation.
- ________ are always suboptimal.
- APAs are generated prior to a perturbation.
- It helps if the perturbation is predictable.
- The perturbation is typically associated with an action by the person.
- APAs produce forces/torques acting against the expected perturbation.
- APAs are always suboptimal.