Direct strain feedback control of flexible robot arms: new theoretical and experimental results

Luo, Zheng-Hua

doi:10.1109/9.262031

Cited by 224 publications

(5 citation statements)

References 27 publications

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“…Broadband vibration control is very attractive if it can suppress all the vibration modes within the control bandwidth, regardless of any changes of the flexible structure under control. If this is possible, the same controller can be applied to any flexible structure, such as beams, plates, and complex structures of many practical machines and vehicles: for example, flexible robot manipulators [1] and smart panels [2,3]. Such a universal controller was proposed by Karnopp [4] and Balas [5], whose idea was an electrical realization of a skyhook damper by feeding a point velocity response back to the collocated point force actuator through a gain, i.e., collocated velocity feedback (CVF).…”

Section: Introductionmentioning

confidence: 99%

Robust broadband vibration control of a flexible structure using an electrical dynamic absorber

Kim¹,

Wang²,

Brennan³

2011

Smart Mater. Struct.

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This paper presents a simple but practical feedback control method to suppress the vibration of a flexible structure in the frequency range between 10 Hz and 1 kHz. A dynamic vibration absorber is designed for this, which has a natural frequency of 100 Hz and a normalized bandwidth (twice the damping ratio) of 9.9. The absorber is realized electrically by feeding back the structural acceleration at one position on the host structure to a collocated piezoceramic patch actuator via an analog controller consisting of a second-order lowpass filter. This absorber is equivalent to a single degree-of-freedom mechanical oscillator consisting of a serially connected mass-spring-damper system. A first-order lowpass filter is additionally used to improve stability at very high frequencies. Experiments were conducted on a free-free beam embedded with a piezoceramic patch actuator and an accelerometer at its center. It is demonstrated that the single absorber can simultaneously suppress multiple vibration modes within the control bandwidth. It is further shown that the control system is robust to slight changes in the plant. The method described can be applied to many other practical structures, after retuning the absorber parameters for the structure under control.

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Section: Introductionmentioning

confidence: 99%

Robust broadband vibration control of a flexible structure using an electrical dynamic absorber

Kim¹,

Wang²,

Brennan³

2011

Smart Mater. Struct.

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“…While the control of manipulators with high link compliance has been addressed in the controls literature, it has been found that many of the solutions presented in the literature are prohibitive in practice. Firstly, mode suppression solutions (as in (Luo, 1993;Sabatini et al, 2012)) that rely on sensors along manipulator links to determine vibrational mode amplitude, frequency, or shape are untenable due to the number of additional sensors required. Space qualified sensors are considerably more expensive than non-qualified sensors (by an order of magnitude in many cases), leading to significant increase in the overall cost of the system.…”

Section: Introductionmentioning

confidence: 99%

Practical Design Considerations for Performance and Robustness in the Face of Uncertain Flexible Dynamics in Space Manipulators

Holmes

2021

Front. Robot. AI

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Low frequency dynamics introduced by structural flexibility can result in considerable performance degradation and even instability in on-orbit, robotic manipulators. Although there is a wealth of literature that addresses this problem, the author has found that many advanced solutions are often precluded by practical considerations. On the other hand, classical, robust control methods are tractable for these systems if the design problem is properly constrained. This paper investigates a pragmatic engineering approach that evaluates the system’s stability margins in the face of uncertain, flexible perturbation dynamics with frequencies that lie close to or within the bandwidth of the nominal closed-loop system. The robustness of classical control strategies is studied in the context of both collocated (joint rate) and non-collocated (force/torque and vision-based) feedback. It is shown that robust stability and performance depend on the open-loop control bandwidth of the nominal control law (as designed for a simplified, rigid plant). Namely, the designed bandwidth must be constrained to be lower than the minimum flexible mode frequency of the unmodeled dynamics by a given factor. This strategy gives credence to popular heuristic methods commonly used to reduce the effect of unmodeled dynamics in complex manipulator systems.

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“…There are other solutions involving infinite dimensional controllers. These includes direct strain feedback controller [12], energy based robust controller [13], proportional, derivative and strain (PDS) controller [14] to mention just but a few.…”

Section: Introductionmentioning

confidence: 99%

“…Block diagram of the inverse system. This figure presents the state space Eqs (12). and(13)as a control system block diagram Filtered inverse control system This figure shows the filtered inverse control system comprising of the filter, the inverse controller and the plant…”

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confidence: 99%

Enhanced vibration control of a multilink flexible manipulator using filtered inverse controller

2018

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Flexible manipulators have numerous advantages such as lightweight, high operation speed, and low power consumption. However, they suffer from link vibrations, especially when operated at high speeds followed by sudden stops. This limitation has been addressed using techniques such as adaptive filters, adaptive strain feedback gain, state feedback control, etc. This article presents a filtered inverse controller for the mitigation of link vibrations in a multilink flexible manipulator. To this end, the plant model, developed and linearized in Maple/Maplesim was inverted in MATLAB. The internal dynamics of the inverse model were stabilized using the state feedback technique. For safe and high-speed operations, the inverse model was augmented with a low pass filter to form the filtered inverse which was used as feedforward controller. Practical experiments were carried out in the dSPACE environment. Results show that filtered inverse controller yield not only faster response but relatively minimal link vibration when compared with the manipulator without vibration controller.

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Direct strain feedback control of flexible robot arms: new theoretical and experimental results

Cited by 224 publications

References 27 publications

Robust broadband vibration control of a flexible structure using an electrical dynamic absorber

Robust broadband vibration control of a flexible structure using an electrical dynamic absorber

Practical Design Considerations for Performance and Robustness in the Face of Uncertain Flexible Dynamics in Space Manipulators

Enhanced vibration control of a multilink flexible manipulator using filtered inverse controller

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