This paper presents a comparison between control/state estimation methods applied on Par2 parallel manipulator for pick-and-place applications as well as a discussion about the mechanical vibrations issue that may become important when reaching very high accelerations. Real-time experiments were performed first to compare two controllers (a linear Proportional-Derivative controller and a nonlinear/adaptive Dual Mode (DM) controller) complied with the same High-Gain Observer (HGO) to estimate articular velocities, and second to compare three state observers (a Lead-lag-based, an Alpha-beta-gamma (ABG) and an HGO) complied with the same nonlinear DM controller. The stability analysis of the Par2 robot under the control of the proposed DM controller (complied with the HighGO for joint velocity estimation) is also provided. Some small mechanical vibrations were noted when reaching 20 G acceleration, which means that it can become an important issue for higher accelerations. Some suggestions are then made for future investigations to avoid/damp these vibrations.
International audienceIn this paper, three control schemes are proposed and experimentally compared on the R4 redundantly actuated parallel manipulator for applications with very high accelerations. First, a proportional-integral-differential (PID) in operational space is proposed to adequately take into consideration the actuation redundancy. Because of its lack of performance, a dual-space feedforward control scheme based on the dynamic model of R4 is proposed. The improvements obtained with this controller allowed the implementation of an experiment, which consisted in the tracking of a trajectory with a maximum acceleration of more than 100G. However, such a controller may have loss of performance in case of any operational change (such as different payloads). Therefore, a dual-space adaptive control scheme is proposed. The stability analysis of the R4 parallel robot when controlled by the proposed dual-space adaptive controller is provided. The objective of this paper is to show that the proposed dual-space adaptive controller not only maintains its good performance independently of the operational conditions but also has a better performance than both the PID and the dual-space feedforward controllers, even when the latter is best configured for the given case (which confirms its applicability in an industrial environment)
This paper deals with the dual-space adaptive control of R4 redundantly actuated parallel manipulator for applications with very high accelerations. This controller is compared experimentally with a dual-space feedforward controller (which may have good performances for specific cases, but has crucial losses of performance when there is any operational change (such as a change of load)), for a pickand-place task with accelerations of 30G (without payload) and 20G (with a payload of 200g). The objective of this paper is to show that the proposed dual-space adaptive controller not only keeps a very good performance independently of the operational case, but also has a better performance than the dual-space feedforward controller even when this last one is best configured to the given case.
Abstract-This paper deals with nonlinear dual mode adaptive control of a redundant manipulator for a pick-andplace scenario with high acceleration (20G). For performance comparisons, a conventional Proportional-Derivative (PD) controller has also been implemented. In this context, the experimental testbed is not equipped with velocity sensors. Therefore, a high-gain observer has been implemented to estimate the articular velocities. Real-time experiments show the performance improvements obtained by the proposed control approach in comparison to the conventional one.
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