11.09.2009 - BIRS: Noise, Time Delay and Balance Control
John Milton
- Inattention appears to "help" balance
- Mechanical time-scales matter
- Stick-balancing appears to be tune to the edge of boundary
- Don't balance it upright, balance slightly off-center
- Random walk with an optimal search
- Non-predictive solution (Maybe stochastic?)
- Continuous control is too expensive
- Suggest a discontinuous "act-and-wait"
- Passive control
- Better off if you wait to cntrol until stability boundary reached
- Increased activation delay corresponds to better performance
- Energy vs Co-energy (How do these correspond to all of the stability studies?)
Bob Peterka
- Observable behavior
- Kinematics
- Ground reaction forces
- EMG response
- Muscle images
- ...neural recordings...
- Experimental and modeling approaches
- Musculoskeletal dynamics
- Sensor dynamics
- Controller
- Internal models
- Head vs Trunk (Thomas Mergner)
- Perception is not perfect
- Head vs Trunk (Thomas Mergner)
- Predictors
- Internal models
- Experiments
- Used a pseudo-random turning sequence to rotational perturbations
- Gain and phase of response to rotational perturbations
- Gain drops off at high frequency
- Phase leads at low frequency and lags at high frequency
- Four modes of control
- Active control
- Integrative control
- Fast-acting control
- Load control
- Delayed proprioceptive feedback
- Positive force feedback (force control)
- Sensory integration feedback (weighted sensory information)
- Rapid response control (springs and dampers)
Valero-Cuevas
- Cool talks located here: http://bme.usc.edu/valero/ENH/ENH-Schedule.html
- Levy Flights
- Long jumps and then a bunch of little jumps
- One way to get levy flights is to have signal-dependent noise (multiplicative noise)
Toro Okihara
- Stochastic resonance - does the shaking make things better?
- Perhaps the shaking helps?
- Non-locality
- Need to look at components interacting instead of each individual component
Ami Radunskaya
- Delay differential equations
- Euler's method can be "exact" as long as the step-size directly divides the delay-length
- dde23 - look-up in matlab
- What about initial requirements on Laplace equations?
- is critically stable in standard spring-mass-damper
- b>q the system is stable in this delayed equation
- To find boundary of stability put in solutions of the form
- Characteristic Polynomial
- Lambda cannot have imaginary solutions with Re>0
- If lambda is purely imaginary:
- Characteristic Polynomial
Lena Ting
- Postural control
- prepatory response (immediate / feedforward)
- short-latency (stretch reflexes) 40 ms
- long-latency (automatic postural response) 100 ms
- decision (steps) 200 ms