Compliant Aerial Manipulators with Dual Arms
The chapter presents the design and modelling of compliant dual arms for aerial manipulation. Physical compliance in the arm joints contributes to increase safety, reliability and robustness of the system during its operation on flight, especially during
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Abstract The chapter presents the design and modelling of compliant dual arms for aerial manipulation. Physical compliance in the arm joints contributes to increase safety, reliability and robustness of the system during its operation on flight, especially during interaction tasks. The chapter also presents validation experiments of the arms mounted on multirotors.
1 Introduction Mechanical compliance is a highly desirable feature for an aerial manipulation robot since it contributes to increases safety, reliability and robustness of the system during its operation on flight, allowing also the estimation and control of the interaction forces and torques by means of the deflection measurement of a flexible element introduced in the joints or links. Most robotic arms designed for aerial manipulation are built with servo actuators that do not provide any torque feedback or control, but they have to be controlled in position [1–3]. This is an important limitation in the application of several model-based control methods that rely on the joint torque control [4, 5]. What is worst, in those operations or tasks that involve physical contact with the environment (grasping, grabbing or impacts) the contact forces introduced at the end effector will be rigidly propagated through the arm links up to the base of the aerial platform, inducing external wrenches that may compromise the stability of the UAV. The unavoidable delay associated to the computations, communications, and due to the servo actuators dynamics (whose control rate is usually below 100 Hz) make in practice very difficult to keep a stiff-joint aerial manipulator stable under A. Suarez (B) · G. Heredia · A. Ollero GRVC Robotics Lab Sevilla, Universidad de Sevilla, Seville, Spain e-mail: [email protected] G. Heredia e-mail: [email protected] A. Ollero e-mail: [email protected] © Springer Nature Switzerland AG 2019 A. Ollero and B. Siciliano (eds.), Aerial Robotic Manipulation, Springer Tracts in Advanced Robotics 129, https://doi.org/10.1007/978-3-030-12945-3_6
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the presence of interaction forces. A compliant joint manipulator instead increases mechanically the tolerance of the system to external wrenches at higher rates than the actuator may provide exploiting the passivity properties of the elastic element [6, 7]. That is, the excess of energy generated during an impact or when there are motion constraints can be stored as elastic potential energy in the compliant joints and released actively controlling the deflection of the flexible element through the position of the servo actuator. The estimation and control of the forces/torques in a compliant joint manipulator is reduced to a position control problem since the deformation of the flexible element, typically a spring or elastomer, is related with the force acting over it. Therefore, measuring the deflection of a compliant joint, it is possible not only to estimate the force acting over it, but also to control it by means of the servo position [8, 9]. Despites the evident benefits of mechan
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