• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2005년도 ICCAS
• /
• pp.1673-1678
• /
• 2005

This paper addresses both theoretical and experimental studies of the stability of haptic interfaces during the simulation of virtual Coulomb friction. The first objective of this paper is to present an analysis of how friction affects stability in terms of the describing function method and the absolute stability theory. Two different feedback methods are introduced and are used to evaluate the analysis: an active force feedback, using a motor, and a passive force feedback, using controllable brake. The second objective of this paper is to present a comparison of the theoretical and experimental results. The results indicate that the sustained oscillations due to the limit cycle occur when simulating friction with an active force feedback. In contrast, a passive force feedback can simulate virtual friction without the occurrence of instability. In conclusion, a hybrid active/passive force feedback is proposed to simulate a highly realistic friction display.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1994년도 추계학술대회 논문집
• /
• pp.938-944
• /
• 1994

Active damping has been shown to offer increased suspension performance in terms of vehicle isolation, suspension packaging, and road-tire contract force. Many semi-active damping strategies have been introduced to approximate the response of active damping with the modulation of passive damping parameters. This study investigates the characteristics of semi-active suspension control through the simulation of passive, skyhook active, and semi-active damping models. A quarter car model is studied with the conrolled damping replacing both passive and active damping. A new semi-active scheme is suggested to eliminate the abrupt changes in semi-active damping force. It is shown that the new strategy performs almost identically to the so called "force controlled" semi-active law without steep changes in damping force or body acceleration.eleration.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
• /
• pp.1124-1127
• /
• 1996

Asymmetric cylinders are usually used as an actuator of active suspensions. Since the force is influenced not only by the control but by the road roughness, force control is needed to track the desired force. But the conventional error feedback control treats the valve-cylinder dynamics at its operating point and many use the symmetric model which differ in all respects. We adopt an asymmetric cylinder model and apply a feedback linearization method for the force control to compensate both the valve nonlinearities and the effects of the road roughness.

• Journal of Magnetics
• /
• 제14권4호
• /
• pp.175-180
• /
• 2009

This paper describes the design and analysis of a tubular linear actuator for intelligent AAP (Active Accelerate Pedal) system. In a driving emergency, the electromagnetic actuator produces an additional pedal force such as the active pedal force and vibration force to release the driver's foot on accelerator pedal. A prior study found that the linear actuator with a ferromagnetic core had a problem in transferring the additional force naturally to a driver due to the cogging force. To reduce the cogging force and obtain higher performance of the AAP system, a coreless tubular linear actuator is suggested. Electromagnetic finite element analysis is executed to analyze and design the coreless tubular actuator, and dynamic analysis is performed to characterize the dynamic performance of the AAP system with the suggested tubular actuator for two types of thrust force.

• Smart Structures and Systems
• /
• 제5권1호
• /
• pp.69-79
• /
• 2009

A non-clipped semi-active stochastic optimal control strategy for nonlinear structural systems with MR dampers is developed based on the stochastic averaging method and stochastic dynamical programming principle. A nonlinear stochastic control structure is first modeled as a semi-actively controlled, stochastically excited and dissipated Hamiltonian system. The control force of an MR damper is separated into passive and semi-active parts. The passive control force components, coupled in structural mode space, are incorporated in the drift coefficients by directly using the stochastic averaging method. Then the stochastic dynamical programming principle is applied to establish a dynamical programming equation, from which the semi-active optimal control law is determined and implementable by MR dampers without clipping in terms of the Bingham model. Under the condition on the control performance function given in section 3, the expressions of nonlinear and linear non-clipped semi-active optimal control force components are obtained as well as the non-clipped semi-active LQG control force, and thus the value function and semi-active nonlinear optimal control force are actually existent according to the developed strategy. An example of the controlled stochastic hysteretic column is given to illustrate the application and effectiveness of the developed semi-active optimal control strategy.

• 한국운동역학회지
• /
• 제32권4호
• /
• pp.121-127
• /
• 2022

Objective: The purpose of this study was to investigate potential effects of transcranial direct current stimulation (tDCS) on bimanual force control capabilities in healthy young adults. Method: Eighteen right-handed healthy young adults (10 females and 8 males; age: 23.55 ± 3.56 yrs) participated in this crossover design study. All participants were randomly allocated to both active-tDCS and sham-tDCS conditions, respectively. While receiving 20 min of active- or sham-tDCS interventions, all participants performed bimanual isometric force control tasks at four submaximal targeted force levels (i.e., 5%, 10%, 15, and 20% of maximal voluntary contraction: MVC). To compare bimanual force control capabilities including force accuracy, variability, and regularity between active-tDCS and sham-tDCS conditions, we conducted two-way repeated measures ANOVAs (2 × 4; tDCS condition × Force levels). Results: We found no significant difference in baseline MVC between active-tDCS and sham-tDCS conditions. Moreover, our findings revealed that providing bilateral tDCS including anodal tDCS on left primary motor cortex (M1) and cathodal on right M1 while conducting bimanual force control trials significantly decreased force variability and regularity at 5%MVC. Conclusion: These findings suggest that providing bilateral tDCS on M1 areas may improve bimanual force control capabilities at a relatively low targeted force level.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2002년도 ICCAS
• /
• pp.90.6-90
• /
• 2002

An active stick which has the variable force-feel characteristics is developed. A combined position and force control strategy is mechanized using a 2-axis built-in force sensor and LVDT. The 2-axis force sensor which measures the stick force felt by the operator is developed by using strain gages and appropriate instrumental amplifiers. A mathematical model of the active stick dynamics is derived, and compared with the experimental results. The frictional torque of the stick due to the mechanical contacts of several parts makes the experimental frequency responses to be dependent on the magnitude of excitation signal, and the precision closed loop control to be difficult. A friction observe...

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2000년도 가을 학술발표회논문집
• /
• pp.377-386
• /
• 2000

Hybrid mass dampers consist of passive tuned mass dampers and active mass dampers. They have the advantage that passive tuned mass dampers are still operated even when active mass dampers are stopped by excessive disturbances or power failure. This paper begins first with the comparative analysis of tuned mass dampers, hybrid mass dampers, and active mass dampers. Next more detailed study is carried out on the hybrid mass dampers: cascade hybrid mass dampers (CHMD) and active tuned mass dampers (ATMD). CHMD is regarded as more reasonable device because of its lighter active mass than ATMD's. However CHMD can not neglect stroke saturation problem caused by the length limitation of active damper mass. We compensate the saturation problem with nonlinear restoring force. The restoring force is calculated based on the states and phases of active mass dampers and added to the control force. It is shown that the presented compensation method prevents CHMD from saturation behavior without apparent changes of control force and responses compared to those in case of not considering the saturation problem.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 추계학술대회논문집
• /
• pp.282-286
• /
• 2000

In this paper, magneto-rheological(MR) damper is studied for vibration control of large infra structures under earthquake. Generally, active control devices need a large control force and a high power supply system to reduce the vibration effectively. Large and miss tuned control force may induce the dangerous situation such that the generated large control force acts to amplify the structural vibration. Recently, to overcome the weaknesses of the active control, the semi-active control method is suggested by many researchers. Semi-active control uses the passive control device of which the characteristics can be modified. Control force of the semi-active device is not generated from the actuator with power supply. It is generated as a dynamic reaction force of the device same as in the passive control case, so the control system is inherently stable and robust. Unlike the case of passive control, control force of semi-active control is adjusted depending on the measured response of the structure, so the vibration can be reduced more effectively against various unknown environmental loads. Magneto-rheological(MR) damper is one of the semi-active devices. Dynamic characteristics of the MR material can be changed by applying the magnetic fields. So the control of MR damper needs only small power. Response time of MR to the input voltage is very short, so the high performance control is possible. MR damper has a high force capacity so it is adequate to the vibration control of large infra structure. Because MR damper has a nonlinear property, normal control method used in active control may not be effective. Clipped optimal control, modified bang-bang control etc. have been suggested to MR damper by many researchers. In this study, sliding mode fuzzy control(SMFC) is applied to MR damper. Genetic algorithm is used for the controller tuning. To verify the applicability of MR damper and suggested algorithm, numerical simulation on the aseismic control is carried out. Simulation model is three-story building structure, which was used in the paper of Dyke, et al. The control performance is compared with clipped optimal control. The present results indicate that the SMFC algorithm can reduce the earthquake-induced vibration very effectively.

• Journal of Magnetics
• /
• 제22권1호
• /
• pp.155-161
• /
• 2017

This paper presents a new nonmechanical rehabilitation system driven by magnetic force. Typically, finger rehabilitation mechanisms are complex mechanical systems. The proposed method allows wireless operation, a simple configuration, and easy installation on the hand for active actuation by magnetic force. The system consists of a driving coil, driving magnets (M1), and auxiliary magnets (M2 and M3), respectively, at the finger, palm, and the center of coil. The magnets and the driving coil produce three magnetic forces for an active motions of the finger. During active actuations, magnetic attractive forces between M1 and M2 or between M1 and M3 enhance the flexion/extension motions. The proposed system simply improves the extension motion of the finger using a magnetic system. In this system, the maximum force and angular variation of the extension motion were 0.438 N and $49^{\circ}$, respectively. We analyzed the magnetic interaction in the system and verified finger's active actuation.