Hyunseok Yang

Improving the vehicle performance with active suspension using road-sensing algorithm

Abstract This paper presents the development of the road-sensing system and its application to active suspension system using preview road information. The road-sensing system which can robustly reconstruct the road input profiles from the intermixed data with the vehicles dynamic motion, is implemented using the composite-sensor system with the optimally shaped transfer function. The performance of this system is evaluated by a series of experimental works in the devised moving-road type simulator. And a real car test equipped with the road-sensing system is performed in the proving ground over both deterministic and random road surfaces. Finally, a controller with preview control scheme based on the 7 degrees of freedom full vehicle model is designed in the frame work of active suspension system, the control performance is evaluated by simulation using the real test road profile data through the road-sensing system.

Normal-Force Control for an In-Pipe Robot According to the Inclination of Pipelines

To move freely, in-pipe robots must be able to adapt to the various geometric changes of pipes. Previously, we described an in-pipe robot that can adapt to changes in diameter and curvature of center curves. This robot is able to estimate the forces exerted on the inner surface of the pipes and balance its posture inside the pipe using angular sensors attached to its rotational joints. In this paper, a method is proposed to estimate the relative attitude between the robots main body and the pipe using the angular sensors attached to a pantograph mechanism. The use of angular sensors makes the structure of the robot simpler and more effective than the use of force or vision sensors because the normal forces and attitude can be estimated from measured angle information. This geometric estimation of attitude relative to the pipes enables the robot to recognize the inclination of the pipes. The PAROYS-II robot can control its normal force according to the variation in pipe inclination. Thus, the proposed method could reduce power consumption and stress on the robots parts. The algorithm has been validated by multiple experiments.

Development of an actively adaptable in-pipe robot

This paper proposes an in-pipe robot adaptable to pipe diameter change. The robot can adapt to 400 to 700 mm diameter piping. A pantograph mechanism provides the adaptability and the robot drives using tracks. One track module consists of front and rear tracks connected by an active joint with structural compliance. Its passive foldable characteristics provide information of the frontal space and help keeping contact with the surface on which it travels. This paper also suggests two control algorithms. One is a method to keeping proper normal force without pressure sensors. The other is a posture control to move in curved pipe by pantograph angle detection. These algorithms are verified by experiment.

Position/vibration control of two-degree-of-freedom arms having one flexible link with artificial pneumatic muscle actuators

Abstract A manipulator with a light and thus flexible link would be advantageous over a rigid link in the sense that it is physically safer when it comes into contact with its environment than a manipulator with a rigid and thus heavy link, even though it is harder for a flexible link manipulator to be robustly controlled. On the other hand, if an actuator can deliver enough force while maintaining proper compliance, it would be advantageous for the sake of safety. An artificial pneumatic muscle-type actuator is an adequate choice in this case. In this work, position control problem of a two-degree-of-freedom arm system having a flexible second link with artificial pneumatic muscle-type actuators is addressed. A composite controller design method is proposed in the framework of the singular perturbation method. Various robust control schemes are designed in order to meet with payload variation, parameter uncertainty, unmodeled vibration mode, actuator dynamics both in the slow and the fast subsystems.

Position and vibration control of a flexible robot manipulator using hybrid controller

In this work, position and vibration control problem of a flexible robot arm with a voice coil type actuator is investigated. For the vibration suppression, a voice coil type actuator is designed and is implemented using H∞ control scheme, in order to guarantee the controlled system robust against unmodeled higher-order mode vibration of the arm, output sensor noise, etc. A fuzzy logic based controller is used for the position and vibration control of the joint hub. Experimental results confirm that the proposed hybrid control scheme of combining fuzzy logic and H∞ controller achieves efficient positioning and vibration suppression performances.

Walking and sit-to-stand support system for elderly and disabled

Walking and sit-to-stand support system, the smart mobile walker, is being developed to help elderly and disabled to live an independent daily life. It comprises almost omnidirectional driving mechanism, sit-to-stand support mechanism, and motion compliance module to control the system. The development and evaluation of basic motion compliance algorithm shows that the algorithm for extraction of user intention from the interaction of the operator and the system determines performance of the system. The required parameters and performance index for improving sit-to-stand function are evaluated by the analysis of force reflection between the operator and the system. Finally, future research topics to improve the performance are addressed

Repetitive controller design for minimum track misregistration in hard disk drives

Repetitive control is a widely used technique for the compensation of repeatable error in systems that contain rotating mechanisms or repeat a trajectory. Generally, it includes delay chains and a low-pass filter in the positive feedback loop, which generate a periodic signal. The controller has typically been implemented in a plug-in fashion and designed heuristically with the simplest form of the filter. However, this design approach is somewhat ambiguous in the selection of controller parameters because of its influence over nonharmonic frequencies. Also, it leaves the possibility for further improvement. This paper presents an improved design method for the repetitive controller that provides minimum track misregistration (TMR) in a hard disk drive (HDD). For TMR prediction, the method identifies disturbances acting on an HDD and estimates servo performance, using the identification result. We have confirmed the identification and estimation procedure through experiments. In our method, first the basic tracking controller is designed and later the repetitive controller is designed in conjunction with a Q filter. A cost function based on Parsevals theorem, reflecting the servo performance as TMR, is defined. Then the servo performance is estimated from the identified disturbance, and the plant and designed controllers frequency response are modified as necessary by changing the parameters of the controller, whose optimization is carried out with a commercial nonlinear optimization tool. The design strategy facilitates the controller design by providing an accurate estimation for the attainable servo performance and design criteria under the optimization framework.

Robust roll control of a vehicle: Experimental study using a hardware-in-the-loop set-up

Abstract This paper presents a simcopy IMulation and experimcopy IMental study of a vehicle with an electrically actuated roll control system. The controller is designed in the framework of an output feedback H∞ control scheme based on the three-degree-of-freedom linear vehicle model. Various parameters which affect the roll dynamics are considered for robust stability and disturbance rejection. In order to investigate the feasibility of the active roll control system, its performance is evaluated by simcopy IMulation in a full vehicle model with non-linear tyre characteristics. After that, an electrically actuated roll control system is devised, which imcopy IMproves the high frequency isolation during inoperative periods. Finally, its performance is investigated by experimcopy IMental work using a hardware-in-the-loop set-up with the devised control system.

Improved Air-Gap Control for SIL-Based Near-Field Recording System

We propose a gap servo method to reduce the overshoot in the near-field (NF) region. In general, we use a mode-switching servo which consists of approach, hand-over, and gap-control modes. However, there is a critical problem, such as an overshoot at the turning point from the approach mode to the hand-over mode, which may cause a collision between the SIL and the disk. In this paper, we propose an improved NF gap servo system using an exponential input in the approach mode which can reduce the overshoot and settling time of the mode-switching servo

Improved Gap Control System Using a Disturbance Observer for Near-Field Recording

In a solid immersion lens (SIL) based near-field recoding (NFR) system which is one of the emerging technologies for next-generation optical data storage systems, it is essential that the air gap between the SIL and the rotating disk is maintained at less than 50 nm without collision in order to obtain the proper coupling efficiency of evanescent waves. To fabricate a reliable near-field air gap servo system, various disturbances such as disk vibration, external shock and overshoot have to be considered, and these possible disturbances have to be prevented effectively. We propose an improved gap servo system using a disturbance observer (DOB), which has a reduced overshoot and rejection performance for the previously mentioned disturbances. The effectiveness of the proposed controller is verified by experimentally. The experiment results, show that the overshoot was reduced using the proposed near-field air gap servo system with a DOB. In the case of the ramp approach mode with and without the hand-over mode in the mode-switching servo, the overshoots were decreased to 50.9% and collision was avoided, respectively. In addition, in the case of the modified approach mode with and without the hand-over mode in the mode-switching servo, the overshoot was decreased to 2.9 and 3.7%, respectively. Consequently, the access time was decreased in each approach case without the hand-over mode using the DOB-based controller. In addition, the disturbance rejection performance of the external shock was improved to 9.11%.