Khalid L. Sorensen

Brief paper: Command-induced vibration analysis using input shaping principles

Input shaping is a well-established technique used for reducing the vibratory response of dynamic systems. Analytical tools are available for systems utilizing input shaping. These tools aid in performance analysis by providing intuitive and computationally simple methods for determining key system attributes, such as the residual vibration in response to a command. This paper describes methods whereby arbitrary reference commands may be interpreted as input-shaped commands. This capability allows input shaping analysis tools to be used on systems without input shapers. Experimental results obtained from an industrial 10-ton bridge crane validate the theoretical developments.

Finite-State Input Shaping

Input shaping is an effective method for suppressing motion-induced oscillation in flexible systems. This technique works well on systems with continuously-variable actuation. However, many systems only have a finite number of actuation states. For example, some relay-driven cranes have three actuation states: off, low-speed, and full speed. The discretizing effect of finite-state actuation can reduce the effectiveness of input shaping. This paper investigates the detrimental effects of discretization. The operational effects of finite-state input shaping are evaluated by using experimental results from a human-operated bridge crane, and a 3-D simulation of this crane.

Operational Effects of Crane Interface Devices

A system for classifying different types of crane motion is presented. The classification system provides a framework to assess the influence that different crane interface devices have on efficiency. The efficiency effects of a joystick, pendent, and experimental visual interface are investigated for certain classes of crane motion. Experimental results suggest that significant efficiency benefits exist for cranes utilizing the visual interface.

Oscillatory Effects of Common Hard Nonlinearities on Systems Using Two-Impulse ZV Input Shaping

Input shaping is an effective method for reducing the oscillatory motion of linear systems. However, hard nonlinearities, such as saturation, rate limiting, backlash, and dead-zone, can reduce the effectiveness of input shaping at suppressing oscillation. This paper quantifies these detrimental effects and presents mitigation strategies.

A CONTROLLER ENABLING PRECISE POSITIONING AND SWAY REDUCTION IN CRANES WITH ON-OFF ACTUATION

Abstract Precise manipulation of payloads is difficult with large cranes. Oscillation can be induced into the lightly damped system by motion of the overhead support point, or from environmental disturbances. A combined feedback and input shaping controller is presented here. The controller uses feedback to detect and compensate for positioning error in the overhead support unit (e.g. the bridge or trolley), and input shaping is used to negate motion-induced oscillation in the payload. The controller is implemented on a 10-ton bridge crane at the Georgia Institute of Technology. The controller generates simple on-off commands, suitable for typical cranes that employ on-off, relay-driven motors. The controller achieves good positioning accuracy, and significant payload sway reduction.

A Multi-Operational-Mode Anti-Sway and Positioning Control for an Industrial Bridge Crane

Abstract A 30-ton industrial bridge crane located at an aluminum sheet manufacturer has been equipped with a crane manipulation system enabling swing-free motion, disturbance rejection, and precise positioning. Previous investigations of anti-sway, positioning, and crane control have yielded important contributions in these areas. These advancements are combined into the unified crane manipulation system described here. An overview of this system is presented, along with experimental results, and a description of how human operators use the crane.

Negative Input Shaping: Eliminating Overcurrenting and Maximizing the Command Space

Input shaping is a filtering method used for reducing oscillation in flexible systems. A class of these filters, called negative input shapers, has been developed to improve system rise-time beyond what is achievable using conventional input-shaping filters. However, negative input shapers can cause overcurrenting and subsequent system oscillation, when used with certain reference commands. This class of reference commands is examined in the context of the command space. The command space represents the space of all possible signals that may be issued to a system. It provides insight into how overcurrenting occurs, how overcurrenting can be mitigated, and the influence that mitigation strategies have on system performance. Two overcurrenting mitigation strategies are presented. The operational effects of overcurrenting and overcurrenting mitigation are evaluated using a three-dimensional simulation of a bridge crane, and experimental results from a 10 ton industrial bridge crane.

Evaluation and integration of a wireless touchscreen into a bridge crane control system

Human manipulation of suspended payloads using cranes can be difficult. Cable sway is easily induced into the lightly damped system, which inhibits efficient, safe, and accurate payload manipulation. This problem is compounded when the payload forms a double-pendulum configuration. To aid operators, a wireless touchscreen controller was integrated into the control system of a 10-ton industrial bridge crane. This touchscreen allows an operator to move freely around the workspace and drive the crane with a simple graphical user interface. The operational effects of the touchscreen was compared to that of a standard pendent interface through a series of human operator performance studies. An oscillation suppression algorithm was used in conjunction with each interface. The touchscreen provides greater operator mobility while producing comparable manipulation performance.

ANALYSIS AND MITIGATION OF DEAD-ZONE EFFECTS ON SYSTEMS USING TWO-IMPULSE ZV INPUT SHAPING

Input shaping is an effective method for reducing oscillatory motion in linear systems. Many physical systems, however, exhibit discontinuous dynamics, such as saturation, rate limiting, backlash, and dead-zone. These hard nonlinearities can degrade the vibration reducing properties of shaped signals. This paper investigates the detrimental effects of dead-zone on a class of input-shaped commands. A mitigation strategy is proposed for reducing these detrimental effects when the value of the deadzone can be estimated. The robustness of this mitigation approach to uncertainties in the dead-zone width is also determined. Theoretical developments are experimentally verified using an industrial 10-ton bridge crane.

Vibration Analysis and Mitigation of Dead-Zone on Systems Using Two-Impulse Zero-Vibration Input Shaping

Input shaping is an effective method for reducing oscillatory motion in linear systems. Many physical systems, however, exhibit discontinuous dynamics, such as saturation, rate limiting, backlash, and dead-zone. These hard nonlinearities can degrade the vibration reducing properties of shaped signals. This paper investigates the detrimental effects of dead-zone on a class of input-shaped commands. A mitigation strategy is proposed for reducing these detrimental effects when the value of the dead-zone can be estimated. The robustness of this mitigation approach to uncertainties in the dead-zone width is also determined. Theoretical developments are experimentally verified using an industrial 10 ton bridge crane. DOI: 10.1115/1.4001818