Joint Angle Measurement Using MEMs Based Inertial Sensors for Biped Robot

The implementation and efficacy of closed loop systems in machines with moving limbs/parts is largely dependent upon the feedback systems that measure the extent of motion - linear or rotational. This paper proposes a novel technique for measurement of joint angles and thus rotational motion for links pivoted at a powered/non-powered joint, using low-cost inertial sensors. The paper proposes the substitution of noisy, inefficient and poor resolution mechanical sensors like optical or pulse encoders with tri-axial accelerometers and tri-axial gyroscope fused in low-cost Inertial Measurement Units(IMUs). This technique is used to measure the angles between the various joints of a bipedal robot and estimate its complete orientation in three dimensional space. The crux of this paper is utilizing the extended capabilities of the inertial sensors in joint angle estimation for closed loop operation of a twelve-Degree Of Freedom(DOF) lower body biped robot with potential implementation on stable bent knee walking on flat surfaces. All the joints of the biped are revolute and facilitate rotation of various limbs like thigh, shin and foot, analogous to a human leg. All links have IMUs mounted on them for the proposed task.