Biped robots could take full advantage of their legged mobility by executing dynamic maneuvers, such as running, jumping, and turning, for obstacle avoidance without sacrificing speed and stability. The objective of this thesis is to design an experimental biped robot that can be used to evaluate and validate different control approaches for performing dynamic maneuvers, focusing specifically on running and jumping.
KURMET is a 5-degree-of-freedom (DOF) planar robot with two articulated legs and a torso. The hip and knee joints are each actuated with an identical series-elastic actuator (SEA), which uses a compliant element in series with a geared brushless dc motor to drive the joint. KURMET is constrained to the wall with a long boom that restricts motion to the sagittal plane. The control electronics and motor amplifiers are mounted on the top of the torso and connect to the off-board power supply with an umbilical cord. A simplified dynamic model of KURMET performing a jump maneuver was developed to aid in the biped design process. A motor thermal model and an alternative SEA design equation were also developed for the design process.
The biped model design variables, which define the system's configuration and performance, were mapped to a set of five critical parameters that included the brushless dc motor, the gearbox, the motor amplifier, the spring constant, and the leg segment length. Each parameter set was evaluated by comparing the jump height and the normalized jump height results from the dynamic model among all the possible sets. KURMET's component level design was broken into the major subsystems, which are the SEA mechanism, the thigh segment, the shank segment, and the torso. The SEA mechanism utilizes an innovative spiral torsion spring design and a unidirectional-SEA concept to achieve series-elasticity in a compact and efficient package. The final biped assembly has a total mass of 14.9~kg. A full support documentation package was developed for KURMET, including a bill of materials and assembly procedures, to aid in the system maintenance.