Robot Arm Control Exploiting Natural Dynamics
This thesis presents an approach to robot arm control exploiting natural dynamics. The approach consists of using a compliant arm whose joints are controlled with simple non-linear oscillators. The arm has special actuators which makes it robust to collisions and gives it a smooth compliant motion. The oscillators produce rhythmic commands of the joints of the arm, and feedback of the joint motions is used to modify the oscillator behavior. The oscillators enable the resonant properties of the arm to be exploited to perform a variety of rhythmic and discrete tasks. These tasks include tuning into the resonant frequencies of the arm itself, juggling, turning cranks, playing with a Slinky toy, sawing wood, throwing balls, hammering nails and drumming. For most of these tasks, the controllers at each joint are completely independent, being coupled by mechanical coupling through the physical arm of the robot. The thesis shows that this mechanical coupling allows the oscillators to automatically adjust their commands to be appropriate for the arm dynamics and the task. This coordination is robust to large changes in the oscillator parameters, and large changes in the dynamic properties of the arm.
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Single degree of freedom motions
Coupling through natural dynamics
6 other sections not shown
amplitude approximately arm dynamics auditory signal ball beat Biological Cybernetics Bode plot cables changes chapter complex compliant configuration connected constant converge coordination coupled oscillator coupled system crank turning damping degrees of freedom describing function analysis drive drumming effect eigenvalues elbow elbow-b entrain equation example exploiting natural dynamics Figure showing fixed points force control graph shows hitting implemented joint angle juggling limit cycle mass mass-spring system Matsuoka oscillator mechanical coupling mechanical system motor natural frequency Neural neural oscillators neurons non-linear oscillator behavior oscillator output oscillator parameters oscillator solution oscillator system oscillatory passive dynamic plot shows posture potentiometer prediction properties pulley Raibert REAL REAL REAL real robot resonance tuning resonant frequency resonant mode rhythmic robot arm robust sensor board series elastic actuators shoulder-b shown in figure sine wave Slinky toy spring stable stiffness strain gauge switching surface task thesis torque torque feedback trajectory transients tube values