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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Extremum-Seeking Gain-Scheduled Adaptive Input Shaping Applied to Flexible-Link Robot) ผู้เขียน: ดร.วิทิต ฉัตรรัตนกุลชัย, รองศาสตราจารย์ ,  Sermsak Chotana, ชลวิทย์ พฤทธพงศ์ สื่อสิ่งพิมพ์:pdf AbstractInput shaping was used to design a finite impulse response (FIR) prefilter. This filter, when convoluted with a reference input, produces a shaped reference input that avoids resonance, resulting in significantly less residual vibration. A flexible system that follows this shaped reference input is able to move from point to point faster due to less settling time. The problem with traditional input shaping is that the filter requires knowledge of the system’s natural frequencies and damping ratios and hence its performance deteriorates when the system is time varying. This paper proposed a novel adaptive input shaping algorithm. The system’s natural frequencies and damping ratios were gain-scheduled based on system-measured states and were simultaneously adjusted by extremum seeking for minimum residual vibration. The proposed algorithm was applied to the point-to-point movement of a one-link, flexible-link robot manipulator whose payload varied with time. The experimental results confirmed the effectiveness of the proposed algorithm, compared with the unadaptive case. |
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หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Vibration Reduction in Slewing of a Very Flexible One-Link Manipulator Using Shaped Reference Inputs) ผู้เขียน:ดร.วิทิต ฉัตรรัตนกุลชัย, รองศาสตราจารย์, กนกศักดิ์ เอี่ยมสมัย, Jitnapa Soontrajarn, Peter H. Meckl สื่อสิ่งพิมพ์:pdf AbstractFuture trends suggest that manipulators will be required to be light and to carry large payloads and this encourages the study of flexible-link robots. However, after more than three decades of investigation, vibration control of the flexible-link robot is still an unsolved problem. Researchers have made much progress using active and passive controls and with structural modification and new sensors and actuators, but a simple, effective and reliable vibration controller has yet to be found. To reduce vibration, shaping the reference input so that no energy is injected around the flexible modes can be performed in the time domain, by convolution of the input with a sequence of impulses or in the frequency domain, by optimally constructing a new input from suitable basis functions. While many researchers have applied the time-domain method to the flexible-link robot, the frequency-domain method is rarely seen with this type of robot. This paper investigated the results of applying the frequencydomain command shaping method to a flexible one-link robot. The closed-loop system consisted of a feed-forward, computed-torque loop and a feedback PID loop. As vital information for this method, the range of natural frequencies with respect to the robot’s parameters was obtained from an exact model, treating the flexible link as an Euler-Bernoulli’s beam. Using minimum a priori knowledge of the robot, the experimental results showed that the method is effective in reducing the vibration of a slewing flexible-link robot. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Reference Input Shaping to Reduce the Move Time of a Very Flexible One-Link Manipulator) ผู้เขียน:ดร.วิทิต ฉัตรรัตนกุลชัย, รองศาสตราจารย์, ธนพล ศรีวงษา, Peter H. Meckl สื่อสิ่งพิมพ์:pdf AbstractWhen a robot manipulator is required to be light, long or to move quickly, its link tends to flex. When the link flexes, its end position is difficult to control. In fact, the flexibility brings about undesirable attributes such as non-minimum phase, tip vibration and complicated dynamics. As a result, in contrast to a rigid-link robot, control of the flexible-link robot is more challenging and is still an open research problem. This study aimed to design a two-degrees-of-freedom control system from a simple model. The controller ensured good tracking and proper disturbance rejection. The closed-loop natural frequency was then computed, with the reference input shaped such that its energy content was low around the natural frequency. The experiment showed that this proposed method reduced tip vibration significantly resulting in a faster move time. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Direct Adaptive Input Shaping Using On-Line Frequency Domain Information and Extremum-Seeking Optimization) ผู้เขียน:ดร.วิทิต ฉัตรรัตนกุลชัย, รองศาสตราจารย์, Sermsak Chotana, ชลวิทย์ พฤทธพงศ์ สื่อสิ่งพิมพ์:pdf AbstractThe input shaping technique convolves the reference command with a properly designed impulse sequence, creating a shaped reference command that avoids exciting the under-damped vibratory system to achieve zero residual vibration on a point-to-point maneuver. The input shaper needs to know the natural frequencies and damping ratios of the vibratory system to design such an impulse sequence. When system configurations change, the natural frequencies and damping ratios also change, and the input shaper must be updated with this new information. In this paper, a point-by-point discrete Fourier transform (DFT) algorithm was used to compute the frequency content of the vibratory signal. The identified natural frequencies were directly updated into the input shaper. Extremum-seeking optimization was used to further adjust the damping ratios for minimal vibration. The proposed technique was applied to a flexible-link robot manipulator. The manipulator was commanded to have a point-to-point maneuver with changing payload. The experimental results, based on cases with or without DFT and extremum seeking, showed that with the proposed technique, minimum residual vibration was obtained even when the payload changed, without having to know the amount of payload. |
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