Results 1  10
of
49
Nonminimum Phase Dynamic Inversion for Settle Time Applications
"... Singletrack hard disk drive (HDD) seek performance is measured by settle time, ts. In this paper, we show the effective use of feedforward dynamic inversion, coupled with reference trajectory yd generation, to achieve high performance ts. Models of HDD dynamics are typically nonminimum phase (NMP) ..."
Abstract

Cited by 17 (15 self)
 Add to MetaCart
Singletrack hard disk drive (HDD) seek performance is measured by settle time, ts. In this paper, we show the effective use of feedforward dynamic inversion, coupled with reference trajectory yd generation, to achieve high performance ts. Models of HDD dynamics are typically nonminimum phase (NMP), and it is well known that the exact tracking solution for NMP systems requires noncausal preactuation to maintain bounded internal signals. In the specific HDD operating modes of interest, anticipation of a seek command is unrealistic, and thus preactuation adds to the overall computation of settle time. Unlike many dynamic inversion tracking applications, this negative effect of preactuation leads to interesting tradeoffs between preactuation delay, yd tracking accuracy, and achievable settle performance. We investigate multiple singleinput singleoutput (SISO) inversion architectures, and we show that the feedforward closedloop inverse (FFCLI) achieves superior settle performance to the feedforward plant inverse (FFPI) in our application because FFCLI does not excite the closedloop dynamics. Using the FFCLI architecture, we further investigate numerous NMP inversion algorithms, including both exact inversion schemes with initial condition preloading and stable approximate NMP inverse techniques. We conclude that the settle performance of the zeroorder Taylor series stable NMP approximation matches the best performance of the exact inversion techniques in our application, and does so without the high frequency excitation required by the Zero Magnitude Error Tracking Controller (ZMETC), or the excessive preactuation required by the Zero Phase Error Tracking Controller (ZPETC). Minimum energy optimal trajectory generation methods show that the system order n is a limiting factor in settle performance. This confirms that the zeroorder series method, which is capable of producing settle times in less than n samples, is on par with optimal approaches yet much simpler to implement. Multiple NMP inversion algorithms are experimentally validated on a Servo Track Writer (STW), which reinforces the general trends observed in ideal simulations.
Optimal Periodic Trajectories for BandLimited Systems
"... Abstract—The speed of an electromechanical scanner is limited by its first resonance frequency. To maximize scan speed, input signals are required that contain negligible frequency components near, or above the first resonance frequency. Such signals are usually obtained by lowpass filtering the de ..."
Abstract

Cited by 9 (7 self)
 Add to MetaCart
Abstract—The speed of an electromechanical scanner is limited by its first resonance frequency. To maximize scan speed, input signals are required that contain negligible frequency components near, or above the first resonance frequency. Such signals are usually obtained by lowpass filtering the desired scan trajectory. However, this introduces curvature and ripple into linear (constant velocity) scan regions. In this work, input signals are designed with guaranteed linear regions and minimal harmonic components above a chosen frequency. The proposed scanning trajectories are proven by simulation and experiment to induce less vibration than existing techniques. Index Terms—Input signal design, mechatronics, motion control, motion planning, nanopositioning, periodic scanning, trajectory design, vibration control. I.
On the Equivalence of Minimum Time Input Shaping with Traditional TimeOptimal Control
 Proc. IEEE Conf. Contr. Appl
, 1995
"... We investigate the constant amplitude nature of several timeoptimM input shaping designs for controlling flexible structures. We first discuss the equivalence of the timeoptimM zerovibration shaper with the traditional timeoptimM control problem. Then we show that several robust timeoptimM shape ..."
Abstract

Cited by 8 (7 self)
 Add to MetaCart
We investigate the constant amplitude nature of several timeoptimM input shaping designs for controlling flexible structures. We first discuss the equivalence of the timeoptimM zerovibration shaper with the traditional timeoptimM control problem. Then we show that several robust timeoptimM shaper designs for flexible systems are equivalent to the timeoptimM controls for different systems. This equivalence allows properties and numericM methods for timeoptimM control problems to be applied to minimum time input shaping design.
Vibration Reduction Using MultiHump ExtraInsensitive Input Shapers
, 1995
"... Input shaping is a method for reducing residual vibrations in computer controlled machines. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with a desired system command to produce a shaped input. The shaped input then becomes the command to the system. Requir ..."
Abstract

Cited by 8 (6 self)
 Add to MetaCart
Input shaping is a method for reducing residual vibrations in computer controlled machines. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with a desired system command to produce a shaped input. The shaped input then becomes the command to the system. Requiring the vibration reduction to be insensitive to modeling errors and system nonlinearities is critical to the success of the shaping process on any real system. Input shapers can be made very insensitive to parameter uncertainty; however, increasing insensitivity usually increases system delays. A design process is presented that generates input shapers with insensitivitytotimedelay ratios that are much larger than traditionally designed input shapers. The advantages of the new shapers are demonstrated with simulations of a simple linear system and simulations of the MACE experimental apparatus.
Design And Implementation Of TimeOptimal Negative Input Shapers
 ASME WINTER ANNUAL MEETING
, 1994
"... Input shaping is a method for reducing residual vibrations in computer controlled machines. Vibration is eliminated by convolving a sequence of impulses, an input shaper, with a desired system command to produce a shaped input. The shaped input is then used to drive the system. The input shaper has ..."
Abstract

Cited by 8 (6 self)
 Add to MetaCart
Input shaping is a method for reducing residual vibrations in computer controlled machines. Vibration is eliminated by convolving a sequence of impulses, an input shaper, with a desired system command to produce a shaped input. The shaped input is then used to drive the system. The input shaper has traditionally contained only positively valued impulses. However, when the impulses are allowed to have negative amplitudes, the length of the shaper can be greatly reduced. Decreasing shaper length is desirable because rise time is limited by shaper length. A simple lookup method is presented that allows the design of negative shapers without the usual requirement of solving a set of simultaneous transcendental equations. Solutions to the problem of highmode excitation that can occur with negative shapers are also presented. The performance of negative shapers is evaluated experimentally.
Comparison of Command Shaping Methods for Reducing Residual Vibration
 Third European Control Conf
, 1995
"... This paper compares command shaping techniques for controlling residual vibration of highperformance machines. Input shaping generates vibrationreducing shaped commands through convolution of an impulse sequence with the desired command. Because input shaping has similarities to notch filtering, i ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
This paper compares command shaping techniques for controlling residual vibration of highperformance machines. Input shaping generates vibrationreducing shaped commands through convolution of an impulse sequence with the desired command. Because input shaping has similarities to notch filtering, it is compared here with a variety of FIR and IIR filters. Several types of input shapers are presented and shown to be more effective than any of the conventional filters. Introduction Control of machine vibration becomes very important as designers attempt to push the state of the art with faster, lighter machines. Many researchers have examined different controller configurations in order to control machines without exciting resonances. Even with a sophisticated controller it is difficult to rapidly move flexible machines without deflections and vibrations. A more achievable goal is to eliminate residual vibration once the machine has achieved a desired setpoint. Input shaping is a comm...
Initial Investigations into the Effects of Input Shaping on Trajectory Following
 American Control Conference
, 1994
"... The effects of input shaping on trajectory following were investigated by simulating the response of a fourthorder system with orthogonal modes and conducting experiments on an XY positioning stage. For nearly all values of damping and frequency ratio, the shaped inputs result in significantly bett ..."
Abstract

Cited by 6 (5 self)
 Add to MetaCart
The effects of input shaping on trajectory following were investigated by simulating the response of a fourthorder system with orthogonal modes and conducting experiments on an XY positioning stage. For nearly all values of damping and frequency ratio, the shaped inputs result in significantly better trajectory following than unshaped inputs. When the trajectory improvement techniques in this paper are used, the shaped inputs perform considerably better for all parameter values. Introduction Input shaping improves settling time and positioning accuracy by reducing residual vibrations in computer controlled machines. The method requires only estimates of the natural frequencies and damping ratios. Input shaping is implemented by convolving a sequence of impulses, an input shaper, with a desired system command to produce a shaped input that is then used to drive the system. The input shaper is determined from a set of constraint equations that limit the residual vibration of the syst...
Inferred EndPoint Control of Long Reach Manipulators
, 1995
"... The problem of the endpoint control of long reach manipulator systems, consisting of a dexterous manipulator carried by deployable structures, is addressed. Such systems can be important where a manipulator must perform a task in a difficult to reach location. Power line maintenance systems and the ..."
Abstract

Cited by 5 (1 self)
 Add to MetaCart
The problem of the endpoint control of long reach manipulator systems, consisting of a dexterous manipulator carried by deployable structures, is addressed. Such systems can be important where a manipulator must perform a task in a difficult to reach location. Power line maintenance systems and the Space Station Freedom's external maintenance robot are examples. Their supporting deployable structures can exhibit substantial vibrations, making the system very difficult to control. Here, a sensor based control algorithm, called Inferred EndPoint Control is proposed. Simulation and experimental results show that it yields stable and accurate manipulator endeffector positioning control despite of vibrations of the system 's supporting structure using easily obtained strain measurements. 1: Introduction This paper addresses the important problem of controlling the motion of a long reach manipulator system (LRMS) that consists of a relatively small, relatively fast manipulator mounted o...
Input Shaping Design For Flexible Systems With Multiple Actuators
 Proceedings of the 1996 IFAC World Congress
, 1996
"... . This paper presents an approach for designing multiinput shapers using an splane pole placement technique. Slightly more information about the system model is taken into account than has been traditionally done with input shaping designs. The input shaping sequences for all system inputs are sol ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
. This paper presents an approach for designing multiinput shapers using an splane pole placement technique. Slightly more information about the system model is taken into account than has been traditionally done with input shaping designs. The input shaping sequences for all system inputs are solved for simultaneously, and the resulting designs lead to shorter impulse sequences than solving for input shaping sequences for each input independently of each other. Keywords. computer controlled systems, feedforward compensation, impulses, insensitivity, linear multivariable systems, modelling errors, oscillation, pointtopoint control, settling times, shaping filters 1. INTRODUCTION This paper addresses rapid feedforward pointtopoint control of flexible structures. The problem of controlling flexible structures is an area of active research, and overviews of recent work can be found in (Book, 1993; Junkins and Kim, 1993). The modal frequencies and damping coefficients of flexible str...
Learning Approximation of Feedforward Control Dependence on the . . .
 IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION
, 1997
"... This paper presents a new paradigm for modelfree design of a trajectory tracking controller and its experimental implementation in control of a directdrive manipulator. In accordance with the paradigm, a nonlinear approximation for the feedforward control is used. The input to the approximation sc ..."
Abstract

Cited by 5 (2 self)
 Add to MetaCart
This paper presents a new paradigm for modelfree design of a trajectory tracking controller and its experimental implementation in control of a directdrive manipulator. In accordance with the paradigm, a nonlinear approximation for the feedforward control is used. The input to the approximation scheme are task parameters that define the trajectory to be tracked. The initial data for the approximation is obtained by performing learning control iterations for a number of selected tasks. The paper develops and implements practical approaches to both the approximation and learning control. As the initial feedforward data needs to be obtained for many different tasks, it is important to have fast and robust convergence of the learning control iterations. To satisfy this requirement, we propose a new learning control algorithm based on the online Levenberg Marquardt minimization of a regularized tracking error index. The paper demonstrates an experimental application of the paradigm to trajectory tracking control of fast (1.25 s) motions of a directdrive industrial robot AdeptOne. In our experiments, the learning control converges in five to six iterations for a given set of the task parameters. Radial Basis Function approximation based on the learning results for 45 task parameter vectors brings an average improvement of four times in the tracking accuracy for all motions in the robot workspace. The high performance of the designed approximationbased controller is achieved despite nonlinearity of the system dynamics and large Coulomb friction. The results obtained open an avenue for industrial applications of the proposed approach in robotics and elsewhere.