Control Of Flexible Arm Research Articles

Vibration Control of Flexible Arm Based on Adaptive Robust Sliding Mode Control and LQR Control

Vibration Control of Flexible Arm Based on Adaptive Robust Sliding Mode Control and LQR Control

P/M Macromolecular Switch Based on Conformational Control Exerted by an Achiral Side Chain within an Axially Chiral Locked Pendant.

Molecular switches, supramolecular chemistry, and polymers can be combined to create stimuli-responsive multichiral materials. Therefore, by acting on the extended/bent conformational composition of an achiral arm, it is possible to create a macromolecular gear, where different supramolecular interactions can be activated/deactivated to control the helical sense of a polymer containing up to five different chiral axial motifs. For this, a chiral allene with a flexible achiral arm was introduced as a pendant in poly(phenylacetylene). Through flexible arm control between extended and bent conformations, it is possible to selectively induce either a P or M helical sense in the polymer, while the relative spatial distribution of the substituents in the allene remains unaltered in two perpendicular planes (configurationally locked). These results show that complex dynamic multichiral materials can be obtained by the polymerization of appropriate monomers that combine chirality, switching properties, and the ability to generate chiral supramolecular assemblies.

Research on High Precision Attitude Measurement of Flexible Link Based on Low Cost Sensors

Flexible links are widely used in industrial robots and special robots due to their light weight, high load ratio and good maneuverability. Due to the flexibility of the connecting rod, the vibration and deformation of the manipulator will occur during the movement, which will affect the stability of the flexible arm. According to the theory of elastic deformation, the attitude of the whole flexible arm can be estimated by indirectly measuring the deformation of the flexible arm. In this paper, low-cost sensors such as encoder, strain sensor and angle sensor are used to measure the deformation of the flexible arm. Through theoretical analysis, the posture and end position of the flexible arm after deformation are obtained. The experimental system is built to verify the proposed method. The results show that the method is correct and effective. The measurement error is 6.5% in the experiment, which meets the measurement accuracy requirements of flexible arm control.

Multiple Model Adaptive Control of Flexible Arm

Multiple Model Adaptive Control of Flexible Arm

Bending moment-based force control of flexible arm under gravity

We discuss the force control problem for a constrained one-link flexible arm with the effect of gravity, based on a distributed parameter model. To solve the force control problem, we propose a simple controller constructed using only the bending moment at the root of the flexible arm. Information about the force and rotational angle of the motor is not necessary for implementation of the controller, and thus a force sensor and encoder are not needed. Several numerical simulations were carried out to determine the performance of the proposed controller, and we found that it works well for force control.

2C33 Motion Control and Optimization of a Ball Throwing Robot with a Flexible Arm(The 12th International Conference on Motion and Vibration Control)

Motion control of flexible arms is more difficult than that of rigid arms. However utilizing its dynamics enables improved performance such as a fast motion in short operation time. This paper investigates a ball throwing robot with one flexible link. This robot throws a ball at a set speed. A mathematical model of this ball throwing robot is derived through Hamilton's principle. The sinusoidal patterns of torque input and structure are designed through the proposed simulation models. The parameters of each torque input pattern and flexible structure are optimized and determined by chaos embedded vector evaluated particle swarm optimization (CEVEPSO). Finally, the residual vibration of the manipulator after throwing is suppressed with input shaping technique.

Accurate position control of a flexible arm using a piezoactuator associated with a hysteresis compensator

In this work, position control of a one-link flexible arm is undertaken by considering the field-dependent hysteresis behavior of a piezoceramic actuator (piezoactuator in short). The proposed arm is controlled by two actuators: a motor mounted at the hub and a piezoceramic bonded to the surface of the flexible link. In the modeling process, two transfer functions: one from the input torque to output hub angle and the other from the input voltage to the output tip deflection are obtained. The hysteretic behavior of the piezoactuator is experimentally identified using the Preisach model, and the first-order descending (FOD) curves are obtained that are required to design a hysteresis compensator. After establishing the overall control block diagram for the position control of the flexible arm, a quantitative feedback theory (QFT) controller is designed by treating parameter variations and external disturbances as uncertainties. Subsequently, a hysteresis compensator that produces additional control input to the piezoactuator is designed to enhance the vibration control performance. An experimental realization of the proposed control scheme is undertaken and the effect of the hysteresis compensator on vibration control of the flexible arm is evaluated in the time domain.

364 ノッチフィルタを用いたサーボ系設計手法と柔軟アームの位置決め制御への応用(GS計測制御2)

364 ノッチフィルタを用いたサーボ系設計手法と柔軟アームの位置決め制御への応用(GS計測制御2)

Theoretical and experimental sensitivity analysis of extra insensitive input shapers applied to open loop control of flexible arm

In this paper, the motion input pre-shaping, applied to flexible manipulators for space applications, is analyzed in terms of sensitivity and robustness to parameters uncertainties. The special environment of space operations and the project specifications lead to the design of manipulators with light and flexible structures. In order to highlight the performances of these methods an open loop control technique is implemented. The control technique is verified by both numerical simulations and experiments. This paper presents the experimental set-up and the results of a series of experimental tests carried out on the space robot simulator assembly, called test-bed for microgravity simulation in robotic arm dynamics (TeMSRAD). The innovative task of the research is to determine experimentally the sensitivity curve for one-hump and two-hump extra-insensitive input shapers, for different vibration limits, by purposely introducing errors in the system model, in order to simulate typical operating conditions.

ISSUES IN THE EXPERIMENTAL IMPLEMENTATION OF THE FAST TIME SCALE CONTROLLER FOR A FLEXIBLE ARM

While several theoretical results on modelling and control of flexible arms have been published in the robotics literature, comparatively less attention has been devoted to design issues related to the practical implementation of these controllers. This work describes a typical single link test bed, discussing the whole path from system identification to controller implementation in the context of two-time scale control. In particular, the design of the fast vibration controller will be addressed, as it represents the most critical part of the system, pointing out technological problems and outlining possible solutions. The discussion will be fully supported by experimental results.

Vibration Control of Flexible Arm by Multiple Observer Structure

This paper describes a vibration control of flexible arm by multiple observer structure using the accelerations of the arm. In general, a flexible arm has several oscillation modes. In case the model of flexible arm can be described as a two-mass resonant system, the reaction torque feedback makes the flexible arm system stable. In the n-mass resonant system, it is known that the reaction torque feedback makes all oscillation modes, only the reaction torque feedback is not enough to make the system stable. The resonance ratio control with the arm disturbance observer has been proposed. The arm disturbance observer is good to suppress the disturbance applied to the tip, but it is not enough to the disturbance applied to other point on the arm.The aim is to make the control system robust against arm inertia variation and disturbance. This paper proposes vibration control of flexible arm by acceleration feedback, and disturbance rejection by multiple observer structure using the accelerations of the arm. The validity of the proposed method is also shown by simulations and experiments.

Nonlinear System Identification and Learning Control of Flexible Arm with one degree of freedom using Neural Networks

This paper studies control methods of a flexible arm with one degree of freedom in order to suppress both vibration due to step movement and residual vibration due to signal noise. When using the conventional PD control methods, these two problems become adverse problems. Namely, the residual vibration becomes large when high gain feedback is used to improve response during suppressing the vibration of the step movement. Moreover, this system becomes a nonlinear system because the deformation of the flexible arm is large by use of soft elastic material. Neural Network (NN) is used as both a simulator and a controller with a view of nonlinear and learning ability. In this study, On-line learning of NN is impossible as the flexible arm breaks by fatigue on many repetitions of learning. Therefore, Off-line learning is employed and the NN simulator is used because of the nonlinear mapping ability for Neuro-controller training. As to the Neuro-controller training, repetitive learning method is proposed, which gives excellent performance of the Neuro-controller by improving both the simulator and controller in turn. This proposed method can give excellent results for the adverse problem of suppressing both the vibration of due to the step movement and the residual vibration due to the signal noise.

ROBUST VIBRATION CONTROL FOR FLEXIBLE ARMS USING THE SLIDING MODE METHOD

ABSTRACTThe vibration control of flexible arms is accomplished here using the sliding mode method, where the traditional discontinuous approach is modified by a differentiable one. The higher order modes of the flexible arm are treated as disturbances and are compensated by introducing a disturbance observer. Simplified expressions of the motor angular and the strain moment for the flexible arm with a disturbance observer are obtained, where the remaining disturbance and the model uncertainties are considered as system uncertainties. The robustness of the sliding mode control is effectively employed to cope with the system uncertainties, where the bounds of the uncertainties are adaptively updated. The proposed control law simultaneously causes the motor angular to track a desired signal and the strain moment to approach zero. The stability of the controlled flexible arm is analyzed based on the obtained important fact that a part of the control input is the approximate estimate of a special signal generated by the uncertainty. The motor angular tracking error and the converging speed of the controlled signals are determined by means of design parameters. Experimental results demonstrate the robustness of the proposed method.

A Method for Vibration Control of Flexible Arms.

This paper presents a method for vibration control system of one-link flexible arms. This method is based on the robust model following control scheme that has been proposed by the authors. This scheme can robustly control the nominal model in the presence of unmodeled dynamics and achieve the desired model following simultaneously. Therefore, this method is suitable for controls of plants that are difficult to model like flexible arms. Furthermore, a sufficient condition for stabilizing the nominal model in the presence of unmodeled dynamics is derived and the existence of bounds for all signals is proved. Finally, the results of computer simulation and flexible arms' vibration control experiment are presented to show the effectiveness of the proposed method.

Virtual passive control of flexible arms with collocated and noncollocated feedback

A novel approach to the control of flexible manipulators is proposed. The controller includes both joint-variable and tip-deflection feedback. It is shown that tip-deflection feedback transforms the original structure into new system in which the structure parameters are virtually scaled up or down. The new system can hence be easily stabilized via a strictly passive feedback law. A co-hub, lumped-parameter structure with multiple massless links is first investigated and stability conditions are developed. The results are then applied to a distributed-parameter flexible arm, which is decomposed into an equivalent lumped-parameter structure via a set of modal functions normalized in a particular way. Tip-deflection feedback is shown to be capable of enhancing control performance on a flexible arm, and stability is ensured as long as the gain associated with the noncollocated feedback satisfies a simple inequality. The stability criteria re valid independent of high-order flexible modes. © 2001 John Wiley & Sons, Inc.

Virtual passive control of flexible arms with collocated and noncollocated feedback

AbstractA novel approach to the control of flexible manipulators is proposed. The controller includes both joint‐variable and tip‐deflection feedback. It is shown that tip‐deflection feedback transforms the original structure into new system in which the structure parameters are virtually scaled up or down. The new system can hence be easily stabilized via a strictly passive feedback law. A co‐hub, lumped‐parameter structure with multiple massless links is first investigated and stability conditions are developed. The results are then applied to a distributed‐parameter flexible arm, which is decomposed into an equivalent lumped‐parameter structure via a set of modal functions normalized in a particular way. Tip‐deflection feedback is shown to be capable of enhancing control performance on a flexible arm, and stability is ensured as long as the gain associated with the noncollocated feedback satisfies a simple inequality. The stability criteria re valid independent of high‐order flexible modes. © 2001 John Wiley & Sons, Inc.

最終スライディングモードによるフレキシブルアームの制振制御

最終スライディングモードによるフレキシブルアームの制振制御

Learning Control of a Flexible Arm by B-spline Curves in Consideration of Time Scaling.

A learning control method using B-spline curves is extended to be applied to the tracking of specified spatial paths at arbitrary speed. This tracking control means the tracking of time scaled trajectories with geomemc path constraints. The proposed method obtains following results : (1) By using Time Scale Factor, dynamics of controlled system is described by two separate terms, a part defining a spatial path and the other one scaling time. (2) An algorithm is proposed to estimat coefficients describing the dynamics. (3) A gain matrix for learning control is expressed as a function of Time Scale Factor. (4) The learning control method is effectively applied to the control of a one-link flexible arm to track arbitrary trajectories which are determined by specifying spatial paths and scaling time.

Load adaptive control of single-link flexible arms based on a new modeling technique

A new method for controlling single-link flexible manipulators is proposed. The objective is to control the tip position of a flexible manipulator in the presence of changes in its payload. Particularly, a new adaptive control system has been designed. The proposed control system requires calculating only one parameter, the tip load, instead of all the transfer functions as in conventional adaptive control methods. The tip load identification algorithm is based on the equivalence existing between a manipulator with payload and a manipulator submitted to the action of external forces. Moreover, this equivalence provides a new technique for modeling these systems which simplifies the methods usually applied. This results in a simple control law that needs minimal computing effort and, thus, can be used for real-time control of flexible arms.

非線形オブザーバを用いたフレキシブルアームの制振制御

非線形オブザーバを用いたフレキシブルアームの制振制御