Impedance Control and Its Adaptive for Hexapod Robot
Impedance control should be generally applied for most robot when contacts some environment to achieve “softness of contact” between the end-effector of robot and the environment. This chapter proposes several algorithms such as impedance control implemen
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Impedance Control and Its Adaptive for Hexapod Robot
Abstract Impedance control should be generally applied for most robot when contacts some environment to achieve “softness of contact” between the end-effector of robot and the environment. This chapter proposes several algorithms such as impedance control implementation for hexapod robot COMET-IV. Also, in the case of heavyweight and large-scale-structured robot, inclinometers from attitude angles should be designed to control the long-term attitudes of the body, not to prevent shaking caused by changes in support of the legs. Moreover, this shaking is considered as a natural scenario since the robot is using hydraulic system and automotive engine. Therefore, only attitude errors that are over the acceptable limit will be included in the adaptive calculation.
7.1
Optimization of Impedance Control Using Virtual Forces from the Body’s Moment of Inertia
Impedance model has potential to be improved in according to three parts in its model, controller input part (force feedback), controller output part (current impedance value), and its parameters value as shown in Fig. 7.1. Therefore, for COMETIV system, optimization has been designed on those mentioned parts based on the robot body posture angles or attitude, instead of using environmental characteristic as done in [1, 2]. Lehtinen has summarized that for the large-scale robot with hexapod configuration, attitude feedback can be used as a torque correction on each leg from the calculation of attitude error that has been filtered by particular dead zone [3]. This is similar to the stable range of posture angle for walking on extremely soft terrain that has been defined and discussed previously in Sect. 6.2. For this adaptive type, inclinometers are derived from moment of inertia of the robot’s body with optimization from Linear Quadratic Regulator (LQR) to correct the impedance control input (for single-leg impedance control) and output (center of mass-based impedance control) directly [4]. As discussed in Sect. 7.4.1, unstable walking on extremely soft terrain contributes to the body swing, which in turn K. Nonami et al., Hydraulically Actuated Hexapod Robots: Design, Implementation and Control, Intelligent Systems, Control and Automation: Science and Engineering 66, DOI 10.1007/978-4-431-54349-7_7, © Springer Japan 2014
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7 Impedance Control and Its Adaptive for Hexapod Robot
Fig. 7.1 Basic impedance model and command optimization focus points
Fig. 7.2 The vertical forces acting on each leg and Euler angles (right hand rotation) along the particular axis based on the BCS (COMET-IV System)
affects the body posture angles or attitude: roll(φ) and pitch(∅) as well as yaw(Ψ ). However, the scope of impedance control described in this study will not be covered for Ψ case since it has been considered in navigation-based walking control in vision-based [5] and teleoperation research studies for COMET-IV [6]. Therefore, in order to include both rotational angles, φ and ∅, in the control system, it is neces
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