| We use Differential Flatness to control Bipedal Robots. We have discovered a special inertia distribution that generates a class of differentially flat bipedal robots and serial chain robots. One of the goals of this work is to formalize paradigms of Design for Differential Flatness. Differential flatness greatly facilitates both of an Planning and Control of Under-Actuated Robots. In general it is hard to generate limit cycles for under-actuated non-linear robots. Differential flatness allows generation of a class of limit cycles. The planning task is formulated as an optimization problem over this class of limit cycles to optimize criterion like energy consumption while satisfying motion constraints like ground clearance. |
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| Single DOF Biped. Hip joint is actuated and contact with ground is revolute and passive. Center of Mass of both the legs is at hip joint. | Three DOF Biped. Hip and Knee joints are actuated and contact wtih ground is passive. COM of the shanks is at the knee joint and combined com of shank and thigh is at the knee joint. | A general bipedal strudcure with more than two segments in each limb. It follows the same recursive mass distribution as the previous two robots. |
| We are currently in the process of fabricating a three DOF biped robot. A CAD model of the robot is shown on the right. The knee joint has a stopper to avoid hyper-extension and there are latches (A) that lock the knee joint after the knee impact. Maxon motors (B) are placed at the hip and they drive the corresponding axis via a pulley (C) and belt arrangement. Counterweights (D) are used to place the center of mass at the respective joints. It is difficult to place encoders at the revolute ground contacts. To measure the inclination of the shank we will be using FAS-G, the inertial measurement unit from MicroStrain. |
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| An Overview of the entire system. |
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