Comparison of polynomial profiles and input shaping for industrial applications

Command shaping creates reference commands that reduce residual vibrations in a flexible system. This thesis examines the use of command shaping for flexible system control in three industrial applications: cam-follower systems, sloshing liquids, and cherrypickers. One common type of command shaping is command smoothing which creates a smooth transition between setpoints. A specific type of command smoothing used in cam-follower systems is the polynomial profile. An alternative technique to reduce vibration in flexible systems is input shaping. In this thesis, input-shaped commands are compared to polynomial profiles for applications requiring both vibration suppression and fast motion. Simulation and experimental results show that input shaping is faster than polynomial profiles and provides a simple approach to suppressing residual vibration. Secondly, significant experimental contributions have been made in the area of slosh control. The oscillation of liquids in a container can cause liquid spillage or can cause stability issues, especially in space vehicles. In the past, a number of control techniques have been proposed, but only a few recommend the use of input shaping. This thesis describes the use of command shaping to limit slosh. Results are supported by numerical and experimental testing. Input-shaped commands reduce residual slosh amplitude compared to unshaped commands and polynomial profiles. Input-shaped commands can also accommodate uncertainties and changes in the sloshing frequencies. Lastly, a small-scale cherrypicker was constructed to study the use of input-shaping control on these types of aerial lifts. Cherrypickers have flexible dynamic effects that can cause dangerous and life-threatening situations. To study this class of machines and to provide future students an experimental testbed, several design criteria were established before construction began. The resulting machine achieved most design objectives, including a simple-to-use graphical user interface and accurate state measurements. Robust input-shaping controllers were implemented to limit endpoint vibration. The design of the cherrypicker is discussed and experimental results are reported.M.S.Committee Chair: William Singhose; Committee Member: Al Ferri; Committee Member: Jun Ued

Multidimensional Trajectories Generation with Vibration Suppression Capabilities: the Role of Exponential B-splines

In this paper, exponential B-spline trajectories are presented and discussed. They are generated by means of a chain of filters characterized by a truncated exponential impulse response. If properly tuned, the filters applied to a vibrating plant are able to cancel the oscillations and in this sense the resulting splines are optimized with respect to the problem of vibrations suppression. Different types of exponential B-spline are illustrated, with one or more exponential filters in the chain, and the procedure for the interpolation of a given set of desired via-points, with a proper choice of the control points, is shown. As a matter of fact, exponential B-splines, generated by means of dynamic filters, combine the vibration suppression capability of input shapers and smoothing filters with the possibility of exactly interpolating some via-points. The advantages of these curves are experimental proved by considering the motion of a spherical pendulum connected to the flange of an industrial robot

Improving Closed-Loop Signal Shaping of Flexible Systems with Smith Predictor and Quantitative Feedback

Input shaping is a technique used to move flexible systems from point to point rapidly by suppressing the residual vibration at the destination. The vibration suppression is obtained from the principle of destruction of impulse responses. The input shaper, when placed before the flexible system inside the control loop, proves to deliver several benefits. However, this so-called closed-loop signal shaping has one major disadvantage that it adds time delays to the closed-loop system. Being a transcendental function, the time delays cause difficulty in analysis and design of the feedback controller. In most cases, the time delays also limit the maximum achievable bandwidth. In this paper, for the very first time, Smith predictors were applied to the closed-loop signal shaping to remove the time delay from the loop. It was shown in simulation result that the detrimental effect of the time delays was completely removed in the case of perfect plant model. The quantitative feedback control was used in the study to quantify the amount of achievable bandwidth and to suppress vibrations from the plant-input disturbance

Input shaping and PID controller for rotary crane

The rotary cranes are widely used in common industrial structures such as construction sites and automotive tracks to transfer loads and materials. The rotary crane controlling process is difficult without method because the motion expected to be faster. One of the current problems in industry and building construction is that rotary cranes became larger and higher. So they need to be faster to achieve acceptable transfer times. But unfortunately, rotary cranes with large structures that are moving at high speed are always associated undesirable payload oscillations resulting from the system dynamics. The purpose of controlling the rotary crane is transporting the load faster without causing any excessive swing at the final position. Rotary cranes have very strong structures in order to lift heavy payloads. The oscillations of the loads must be reduced to prevent hazards for people and equipment in the work place. In this work, two types of controllers are studied which is input shaping and PID controller. The input shaping controller and PID controller is developed to control the horizontal motion of pendulum and arm position in rotary cranes to reduce the sway angle of the rope to its set point during the transportation process and time response specification. It is developed to control the sway of load to correcting the radial and rotational motion of cranes and the oscillation damping PID controllers for damping the oscillation angles of the loads. LabVIEW and MATLAB software was used to develop input shaping and Proportional Integral Derivative (PID) controller and to simulate the system response. The simulation results demonstrate the effectiveness of the proposed method

Control oriented modelling of an integrated attitude and vibration suppression architecture for large space structures

This thesis is divided into two parts. The main focus of the research, namely active vibration control for large flexible spacecraft, is exposed in Part I and, in parallel, the topic of machine learning techniques for modern space applications is described in Part II. In particular, this thesis aims at proposing an end-to-end general architecture for an integrated attitude-vibration control system, starting from the design of structural models to the synthesis of the control laws. To this purpose, large space structures based on realistic missions are investigated as study cases, in accordance with the tendency of increasing the size of the scientific instruments to improve their sensitivity, being the drawback an increase of its overall flexibility. An active control method is therefore investigated to guarantee satisfactory pointing and maximum deformation by avoiding classical stiffening methods. Therefore, the instrument is designed to be supported by an active deployable frame hosting an optimal minimum set of collocated smart actuators and sensors. Different spatial configurations for the placement of the distributed network of active devices are investigated, both at closed-loop and open-loop levels. Concerning closed-loop techniques, a method to optimally place the poles of the system via a Direct Velocity Feedback (DVF) controller is proposed to identify simultaneously the location and number of active devices for vibration control with an in-cascade optimization technique. Then, two general and computationally efficient open-loop placement techniques, namely Gramian and Modal Strain Energy (MSE)-based methods, are adopted as opposed to heuristic algorithms, which imply high computational costs and are generally not suitable for high-dimensional systems, to propose a placement architecture for generically shaped tridimensional space structures. Then, an integrated robust control architecture for the spacecraft is presented as composed of both an attitude control scheme and a vibration control system. To conclude the study, attitude manoeuvres are performed to excite main flexible modes and prove the efficacy of both attitude and vibration control architectures. Moreover, Part II is dedicated to address the problem of improving autonomy and self-awareness of modern spacecraft, by using machine-learning based techniques to carry out Failure Identification for large space structures and improving the pointing performance of spacecraft (both flexible satellite with sloshing models and small rigid platforms) when performing repetitive Earth Observation manoeuvres

HYBRID POSITION AND VIBRATION CONTROL OF NONLINEAR CRANE SYSTEM

This paper presents comparative assessments of input shaping techniques using two different approaches, for sway reduction of cranes system. First, the shaper was designed at maximum load hoisting length while the second was designed at average load hoisting length. These were accomplished using curve fitting toolbox in MATLAB. In both case; Zero Vibration (ZV), Zero Vibration Derivative (ZVD) and Zero Vibration Derivative Derivatives (ZVDD) were designed. Average hoisting length (AHL) shapers performed better than the Maximum hoisting length (MHL) shapers. Proportional integral derivative (PID) was incorporated for position control. After successful implementation, Simulation results show that a precise payload positioning was achieved. AHL-ZVDD has superior performances in sway reduction and robustness.

Sway Reduction of Tower Crane

Tower crane is a common fixture at any major construction site. They often rise hundreds of feet into the air, and can reach out just as far. Tower crane has a problem that a fast transfer of the load causes sway of the load. It takes a long time sometime to lift up and unload the load due to the wind and other disturbances. The objective of this project is to minimize the sway of the load suspended on the tower crane by developing a control method by using a concept of spherical pendulum and delayed position feedback. Develop equation for controller and solve using numerical simulation. From the result gained, the best method can be used to minimize the sway of the tower crane

Bibliography of Supersonic Cruise Research (SCR) program from 1977 to mid-1980

The supersonic cruise research (SCR) program, initiated in July 1972, includes system studies and the following disciplines: propulsion, stratospheric emission impact, structures and materials, aerodynamic performance, and stability and control. In a coordinated effort to provide a sound basis for any future consideration that may be given by the United States to the development of an acceptable commercial supersonic transport, integration of the technical disciplines was undertaken, analytical tools were developed, and wind tunnel, flight, and laboratory investigations were conducted. The present bibliography covers the time period from 1977 to mid-1980. It is arranged according to system studies and the above five SCR disciplines. There are 306 NASA reports and 135 articles, meeting papers, and company reports cited

Liikkuvien työkoneiden värähtelyn vaimennus painetakaisinkytkennällä

In this thesis a hydraulically driven wheel loader, which has a flexible crane mounted in front of the machine, has been under research. Flexible boom was excited with a operator given commands, which caused the system vibrate due to different sources of flexibility. The goal was to test cylinder load pressure as a estimate of boom vibrations and use it as a feedback signal to suppress the system oscillations. Therefore, a simulation of wheel loader was created, which replicates real four wheel loader located at the facilities of Laboratory of Automation and Hydraulics. The first simulator represents a traditional hydraulical system, which has proportional directional valves and variable displacement pump with load sensing functions. A simple controller with pressure feedback vibration damping was designed and tested with different scenarios. After promising results, another simulator was created, which emulates the existing wheel loader better. This experimental wheel loader, called as IHA-machine, has different directional valves and pump operating principal. For working hydraulics, a digital flow control unit was installed. As a power source, IHA-machine has a variable displacement pump-motor, which has a possibility to collect energy from hydraulic system. Updated simulation version was tested with a controller, which was able to control flow and supply pressure. Vibration damping was added to the flow controller and tested in simulator. After this, the same controller was also tested in real IHA-machine. The results showed, that load pressure as an estimate of system vibrations is a promising way to damping the oscillations that exist in the application. However, the simulation results couldn't be repeated at the same level in the real machine. The control of boom with flow in digital valve environment appeared to be a difficult task when vibration damping was implemented. Regardless, some oscillation canceling was still achieved