Unknown Dead-zone Research Articles

Adaptive Control of a Class of Nonlinear Systems with Unknown Dead-Zones

An adaptive control design is proposed for systems with an unknown dead-zone at the input of a smooth nonlinear dynamics which can be transformed into the parametric-strid-feedback form. The adaptive controller contains an adaptive dead-zone inverse to cancel the dead-zone and is designed using the backstepping method for adaptive nonlinear control. The adaptive control scheme ensures closed-loop signal boundedness.

Discrete-time adaptive control of plants with unknown output dead-zones

For discrete-time plants with unknown dead-zones at the output we propose a new controller structure with an adaptive dead-zone inverse. We consider two control problems; one when only the dead-zone is unknown, and the other when the whole plant is unknown. We allow the dead-zone to be with unequal slopes. The proposed controller structure results in a linear parametrization which is crucial for developing adaptive update laws. We prove the signal boundedness for the closed-loop system, and for a special case we establish asymptotic tracking. Simulation results show that our adaptive control schemes improve system performance.

Discrete-time adaptive control of systems with unknown deadzones

An adaptive deadzone inverse approach is developed for control of discrete-time systems with unknown deadzones at the input of linear dynamics. The proposed controller consists of an adaptive deadzone inverse, whose parameters are updated to cancel the effect of the deadzone, and a linear part, which is designed to achieve tracking of a reference signal by the system output. When the linear part of the system is known, its parameters are used to specify the parameters of the linear part of the controller. When the linear part of the plant is unknown, the linear control parameters are adaptively estimated. The control error caused by the adaptive deadzone inverse is expressed as a linearly parametrizable part plus a bounded disturbance. Adaptive laws which employ parameter projection are used to update the controller parameters. They are robust with respect to the bounded disturbance, and they result in parameter estimates needed to implement an adaptive deadzone inverse. We prove the closed-loop signal bo...

018 Adaptive control of plants with unknown output dead-zones

018 Adaptive control of plants with unknown output dead-zones

A two-layered fuzzy logic controller for systems with deadzones

Existing control methods do not perform well when applied to systems containing nonlinearities arising from unknown deadzones. In particular, we show that a usual fuzzy controller applied to a system with a deadzone suffers from poor transient performance and a large steady-state error. In this paper, we propose a novel two-layered logic controller for controlling systems with deadzones. The two-layered control structure consists of a logic-based precompensator followed by a usual PD controller. Our proposed controller exhibits superior transient and steady-state performance compared to usual PD controllers. In addition, the controller is robust to variations in deadzone nonlinearities. We illustrate the effectiveness of our scheme using computer simulation examples. >

Adaptive control of plants with unknown dead-zones

Model reference adaptive controllers are designed for plants with unknown dead-zones. Several control strategies are investigated in which two sets of adjustable parameters, one belonging to a dead-zone inverse and the other to a linear controller, are either kept fixed or adaptively updated. The developed adaptive control schemes ensure boundedness of all closed-loop signals and reduce the tracking error.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Adaptive Control of Plants with Unknown Output Dead-zones

For plants with unknown dead-zones at output we propose a new controller structure with an adaptive dead-zone inverse. We consider two control problems: one when only the dead-zone is unknown and the other when the whole plant is unknown. We allow the dead-zone to be with unequal slopes. The proposed controller structure results in a linear parametrization which is crucial for developing adaptive update laws. We prove the signal boundedness for the closed-loop system, and for a special case we establish asymptotic tracking. Simulation results show that our adaptive control schemes improve system performance.

Fuzzy Precompensation of PD Controllers For Systems with Deadzones

Simple conventional control methods, such as PD and PID controllers, are widely used in industrial applications. Such controllers exhibit poor performance when applied to systems containing nonlinearities arising from unknown deadzones. In this article, we propose a novel fuzzy logic-based precompensation approach for controlling systems with deadzones. The control structure consists of a fuzzy logic-based precompensator followed by a conventional PD controller. Our proposed control scheme shows superior transient and steady-state performance compared to conventional PD and PID controllers. In addition, the scheme is robust to variations in deadzone nonlinearities, as well as the steady-state gain of the plant. We illustrate the effectiveness of our scheme using computer simulation examples.

Adaptive Control of Rotary System with Nonlinear Frictions.

This paper is concerned with the design of a Model Reference Adaptive Control System (MRACS) for motion with unknown nonlinear frictions. From the control system viewpoint, the static friction and Coulomb friction are characterized by a nonlinear deadzone element and constant disturbance for the control input signal, respectively. Then, the MRACS for the nonlinear frictions is considered for a nonlinear system which is a cascade combination of an unknown deadzone block or disturbance and a linear dynamic block. In order to verify the validity of the theoretical results, the design method described above is applied to a servo system influenced by friction. Experimental results show the high performance of the constructed MRACS and the effectiveness of the proposed method.

Adaptive Control of Rotary System with Unknown Dead Zone.

This paper is concerned with the design of a Model Reference Adaptive Control System (MRACS) for motion with unknown nonlinear friction. From the control system viewpoint, the static friction is characterized by a nonlinear dead zone element for the control input signal. Thus, the MRACS is considered for a nonlinear system which is a cascade combination of an unknown dead zone block and a linear dynamic block. In order to verify the validity of the theoretical results, the design method described above is applied to a servo system influenced by friction. Experimental results have shown the high control performance of the constructed MRACS and the effectiveness of the proposed method.

Identification of multivalued and memory nonlinearities in dynamic processes

This paper presents a new approach to the identifica tion of multivalued and memory types of functions (such as hysteresis) in a class of nonlinear dynamic processes which can be represented by a set of ordi nary differential equations. This approach leads to the direct identification of an unknown nonlinear coefficient or unknown nonlinear term. Four examples illustrate applications of the method: a hysteresis loop, a relay with hysteresis, a second-order system with hysteresis and an unknown nonlinear "constant," and a relay with hysteresis and an unknown dead zone. This paper uses standard CSMP function notation. The four systems were simulated and identified with adequate accuracy for many engineering purposes. The method is applicable to a broad class of mechan ical processes and dynamic mechanisms, including many common vibration phenomena involving nonlinear springs and nonlinear energy dampers. A CSMP digital computer program was used to simulate the dynamics of the physical systems and to implement the identifica tion technique.