Centimeter-Level Aerial Assembly Achieved With Manipulating Condition Inference and Compliance

This article develops a compliant control strategy for the aerial manipulation of high precision, which is easy to deploy and transplant between the simulation and the real system. To facilitate this development, a nominal dynamic model of the aerial manipulation system is first formulated by taking the attitude as a low-level control loop. On this basis, all lumped uncertainty is treated as a possible dynamic variation of undetermined term. This undetermined dynamic variation is then iteratively inferred from the deviation between nominal model prediction and state measurement in real time. A finite impulse response filter is also proposed to attenuate measurement noises while avoiding undesired phase lags. With inference results, a compensation controller is designed accordingly for the airframe to establish a stable base-platform. Subsequently, a kinematic compensation, handling possibly residual fluctuation of the airframe, is further implemented for the manipulator to enhance the performance. Simulations and experiments are carried out at last, and the controller is illustrated to be quickly deployable with a stand-alone onboard computer mounted on a common airframe. Results demonstrate that aerial manipulator can reliably fetch and assemble a concerned part from different orientations in holes of 0.015-m radius, i.e., the precision of the end-effector is in centimeter level, which outperforms the state-of-the-art.