Dynamic Feedforward Control Research Articles

A dynamic feedforward control approach for a semi-active damper based on a new hysteresis model

AbstractIn this paper a dynamic feedforward control approach for a continuously variable hydraulic semi-active damper of a vehicle suspension is presented. It takes into account dynamic effects in the damper force generation by employing a new hysteresis model. The hysteresis model describes the damper behavior considerably better than static characteristics do. The latter resemble the state of the art for the calculation of the control inputs of semi-active dampers in order to track reference forces from higher level suspension controllers. The low complexity of the hysteresis model enables its real time capability and thus the applicability of the damper control approach. The performance of the concept is validated in experiments on a quarter-car test rig by comparing the dynamic control approach with the static characteristic based control using a skyhook controller and a linear optimal regulator. The new dynamic feedforward controller especially improves ride safety by enabling better force tracking in the range of the wheel resonance frequency.

A kinematic analysis of visually-guided movement in Williams syndrome

Previous studies have reported that people with the neurodevelopmental disorder Williams syndrome exhibit difficulties with visuomotor control. In the current study, we examined the extent to which visuomotor deficits were associated with movement planning or feedback-based on-line control. We used a variant of the Fitts' reciprocal aiming task on a computerized touchscreen in adults with WS, IQ-matched individuals with Down syndrome (DS), and typically developing controls. By manipulating task difficulty both as a function of target size and amplitude, we were able to vary the requirements for accuracy to examine processes associated with dorsal visual stream and cerebellar functioning. Although a greater increase in movement time as a function of task difficulty was observed in the two clinical groups with WS and DS, greater magnitude in the late kinematic components of movement—specifically, time after peak velocity—was revealed in the WS group during increased demands for accuracy. In contrast, the DS group showed a greater speed-accuracy trade-off with significantly reduced and more variable endpoint accuracy, which may be associated with cerebellar deficits. In addition, the WS group spent more time stationary in the target when task-related features reflected a higher level of difficulty, suggestive of specific deficits in movement planning. Our results indicate that the visuomotor coordination deficits in WS may reflect known impairments of the dorsal stream, but may also indicate a role for the cerebellum in dynamic feed-forward motor control.

Inverse Dynamics Modeling and Nonlinear Controller Design of the Similar Model of a Forging Manipulator

Forging manipulator is one of the most important equipment in the automation of forging operation,and plays an important role in improving productivity and ensuring manufacturing quality. To improve the forging manipulator's performance,a similar model of a forging manipulator is designed to facilitate experiments. The inverse dynamics of this similar model is obtained by using the principal of virtual work;and to decrease the negative effect of the nonlinearity of the mechanism dynamics,the dynamic feedforward control method is adopted,distributing driving forces,which are needed for the tongs carrier of the manipulator to generate desired motions,to each hydraulic cylinder. The tracking performance of the tongs carrier is chosen to be guaranteed by improving the position response performance of each hydraulic cylinder. So,by using feedback linearization method and considering the nonlinearities of hydraulic systems,a hydraulic cylinder system is transformed into a second-order linear system which can be easily adjusted by setting four parameters to get desired damp ratio and natural frequency and to improve the response dynamics. Simulation results finally attest the validity of the proposed method.

Motion control of the 2-DOF parallel manipulator of a hybrid machine tool

SUMMARYThis paper focuses on the motion control of the two-degree-of-freedom (2-DOF) planar parallel manipulator of a hybrid machine tool. On the basis of the performance analysis of the kinematic control system, a parameter-tuning method is proposed for regulating the control parameters. To improve the response performance, the proportional-derivative control and a low-pass filter are introduced to the position-loop controller. The simulation shows that the response speed is increased and that the tracking error is reduced. Furthermore, the effect of load torque on the contour error is investigated, and the dynamic feedforward control is used to control the parallel manipulator. On the basis of the principle of dual-channel compensation, the feedforward compensator is designed. The simulations, that the moving platform moves along a linear trajectory and circular trajectory, show that the dynamic feedforward control can reduce the effect of load torque on contour error.

Application of pH-ORP titration to dynamically control the chlorination and dechlorination for wastewater reclamation

An automatic pH–ORP (oxidation–reduction potential) titration device was developed and applied to dynamically control the wastewater chlorination and dechlorination doses in this study. In the pH–ORP titration and back-titration process, the monitoring peaks and valleys on the pH and ORP profiles could indicate the influent concentrations of chlorine-consumed materials (mainly ammonia nitrogen for chlorination) and residual chlorines (for dechlorination). The required chlorination dose can be optimized by multiplying the identified ammonia concentration to the optimal Cl/N ratio (chlorine to ammonia nitrogen weight ratio). The required dechlorination dose was also found to be correlated to the residual chlorine concentration with linear relationship. Therefore, an innovative and dynamic feed-forward dose control strategy was proposed. Finally, a series of continuous wastewater chlorination and dechlorination experiments were conducted to evaluate this proposed control strategy. Two control factors, CF C and CF D , were also used to regulate the doses to meet the water qualities for different wastewater reclamation proposes. The experimental result has shown that both chlorination and dechlorination doses were effectively controlled, and appropriate disinfection efficiencies and remaining chlorine residuals in effluent were achieved.

Dynamic feed-forward control of a parallel kinematic machine

This paper deals with the dynamic feed-forward control of a 6-UPS parallel kinematic machine (PKM). The control system consists of the closed-loop control subsystem and the dynamic control subsystem. The closed-loop control subsystem is constructed by using the PD control and low-pass filter. Moreover, zero phase error tracking control (ZPETC) is introduced to the closed-loop control subsystem to improve its response capability. Based on the rigid-body dynamic model of the PKM, the dynamic control subsystem is designed by using the computed torque control and feed-forward control. Since the phase lag of the closed-loop control subsystem is almost eliminated by ZPETC and PD control, the motion precision of the closed-loop control subsystem is improved largely. The influence of the dynamic characteristic of the PKM on the motion precision is decreased due to the introduction of rigid-body dynamic model into the control system. As a result, the motion precision of the moving platform is greatly improved.

Stability Analysis in Homogeneous Charge Compression Ignition (HCCI) Engines With High Dilution

This paper analyzes the stability of the autoignition process of homogeneous charge compression ignition (HCCI) engines with exhaust dilution. We find conditions under which steady-state multiplicity exists with stable and unstable equilibria. This analysis is conducted taking into account the internal feedback structure of the thermal dynamics. Specifically, HCCI combustion timing determines the combustion heat produced and is determined by the heat provided through high internal exhaust gas recirculation from the previous combustion cycle. It is shown that the thermal equilibria are characterized by a simple returning map consisting of two curves, namely the breathing temperature curve and the combustion temperature curve. The influence of heat transfer and the cooling system in the system stability is also analyzed. The returning map and the stability of the multiple steady-state equilibria are confirmed with a high-order dynamic nonlinear model. The high-order dynamic model includes manifold filling and composition dynamics and has been validated both at steady state and during transient. It is shown that a static feedforward controller can cause instability during switching from a high to a low load. A dynamic feedforward controller, on the other hand, is able to stabilize the transition by reducing temperature excursions and, hence, keeping the temperature trajectories within stable regions

Crosswind Feedforward Control – A Measure to Improve Vehicle Crosswind Behaviour

SUMMARY The theory of crosswind feedforward control was explained using the example of a vehicle with active front-wheel steering. Beforehand, the calculation formulas and frequency responses of the transient crosswind force and of the wind yaw moment acting on the vehicle were derived using the example of a simple vehicle fluid model. The influence of the transiency of crosswind disturbance on the dynamic crosswind behaviour of a vehicle was then presented. The results of simulation confirmed the analyses carried out in the frequency domain for feedforward control with front, rear and all-wheel steering. With front-wheel steering, the influence of crosswind on one of the vehicle movement variables (lateral acceleration or yaw rate) could be almost completely compensated by dynamic feedforward control. With rear-wheel steering, it is only possible to compensate directly for the influence on the yawing rate. Due to the setting of the side force in the same direction as the lateral wind force at the start, ...

Sharp Corner Tracking Using the IKF Control Strategy

Due to the increasing demand for higher precision in manufacturing, there has been a recent tendency to complete the conventional proportional position controller of numerical control (NC) with an additional dynamic feedforward controller to compensate for tracking errors. Laboratory results have proved that this goal can be reached when all the P-position controller characteristics have been kept. This concept, therefore, is expected to be found soon in many new control systems. This paper introduces such a compensation method and shows its productive capacity through analysis and experimentation.

Multiloop, feedforward, modal and optimal control of an evaporator

The goodness of the ‘classical’ multiloop, dynamic feedforward, modal and optimal control methods, as approaches to multivariable regulatory control, are evaluated on the basis of the experience obtained by designing and experimentally implementing control systems on a double effect pilot plant evaporator. A fifth order state space model is used in the theoretical designs. The criteria used in evaluating the goodness of a control method are the soundness of its principles, its synthesis power and the demands for sophistication in actual implementation.

Computer modelling and control of manufacturing systems with particular reference to the tailoring industry

There is considerable potential for computers integrated in the manufacturing process at factory and shop-floor level. In particular, owing to their current low price, minicomputers are attractive for use in realtime interactive computer-aided control systems where the supervisory staff are a significant part of the control system. Computers tend to have a low-level of application in a systems engineering sense, i.e. they are typically used for stock control, cataloguing and data processing, which are only elements of a control system. There is much to be done in high-level dynamic feedforward control to help management by incorporating forecasting techniques with manufacturing-system models and assessments of current system state in a dynamic and interactive manner. If this potential can be realised by incorporating computer hardware, visual data-display terminals and information collection devices into the man/machine manufacturing process, then management will be more able to carry out their roles. Complex automation of the factory is not being proposed. On the contrary, it is believed that an appreciation of the computer-system limitations, coupled with the need to exploit modern control theory and computing techniques, will lead to systems in which the key controlling role of the supervisors will be strengthened, becoming dominant and more satisfying. The computer will handle the details of information searching and processing. The man will be the controller. This paper summarises and clarifies techniques by which higher forms of control might be realised.

A Nuclear Reactor DDC Using a Microcomputer

This paper describes the implementation objectives, methods, results and problems behind an experiment to control a one megawatt pool reactor with a digital microcomputer. The Direct Digital Controller (DDC) was built to investigate the uses and advantages of microcomputer systems in process control applications. New features include: operator oriented displays, dynamic feedforward control for improved transient performance, system safety checks, online self-diagnostics and maintenance aids.