• The Journal of Korea Robotics Society
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• v.4 no.4
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• pp.273-280
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• 2009

It is difficult to find a practical solution for the backward-motion control of a car-like mobile robot with n passive trailers. Unlike an omni-directional robot, a car-like mobile robot has nonholonomic constraints and limitations of the steering angle. For these reasons, the backward motion control problem of a car-like mobile robot with $n$ passive trailers is not trivial. In spite of difficulties, backing up a trailer system is useful for parking control. In this study, we proposed a mechanical alteration which is connecting $n$ passive trailers to the front bumper of a car to improve the backward motion control performance. Theoretical verification and simulations show that the backward-motion control of a general car with n passive trailers can be successfully carried out by using the proposed approach.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1190-1195
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• 2003

In this paper, it is shown how a robot with n passive trailers can be controlled in backward direction. When driving backward direction, a kinematic model of the system is represented highly nonlinear equations. The problem is formulated as a trajectory following problem, rather than control of independent generalized coordinates. Also, the state and input saturation problems are formulated as a trajectory generation problem. The trajectory is traced by a rear hinge point of the last trailer, and reference trajectories include line segments, circular shapes and rectangular turns. Experimental verifications were carried out with the PSR-2(public service robot $2^{nd}$ version) with three passive trailers. Experimental result showed that the backward motion control can be successfully carried out using the proposed control scheme.

• The Journal of Korea Robotics Society
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• v.5 no.4
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• pp.286-293
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• 2010

The trailer system offers efficiency of transportation capability. However, it is difficult to control the backward motion. It is an open loop unstable problem. To solve this problem, we are proposed the driver assistance system. Driver assistance system assists a driver to control the backward motion of trailer system as if forward motion. A driver only secure the rear view of last passive trailer, and select the control input to drive the last passive trailer. The driver assistance system converts the control input of the driver into velocity and steering angle of the vehicle using the inverse kinematics. It is possible by electronic control input devices and the rear view camera. Effectiveness of driving assistance system is verified by the simulation and the experiments.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.11-15
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• 2000

This paper provides a basic study on automatic of a trailer type vehicle which consists of two parts such as a tractor and a trailer Backward moving and parking control is very important to automate this type of vehicle. However it is very difficult to control such their motion since a trailer type vehicle is a non-holonomic system. Therefore in this paper we propose the backward path tracking control algorithm for a trailer type vehicle. And also this paper presents the results of simulation to verify the effectiveness of the proposed control algorithm.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.1
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• pp.124-130
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• 2001

This paper presents a methodology on automation of a trailer type vehicle which consists of two parts: a tractor and a trailer. Backward moving and parking control is very important to automate this type of vehicle. It is difficult to control the motion such a trailer vehicle whose dynamics in non-holonomic. Therefore, in this paper, the modeling and parameter estimation of the system using a RCGA(real-coded genetic algorithm) is proposed and a backward path tracking control algorithm is then obtained. The simulation results verify the effectiveness of the proposed method.

• Journal of Biosystems Engineering
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• v.20 no.1
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• pp.87-94
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• 1995

When farmer loads and unloads farm products with a trailer, linked to a tractor, the tractor-trailer is backed up to the loading duck. However, travelling backward is not easy and takes a time for even skilled operators. Therefore, unmanned backing up is necessary to save the effort. A backward controller of tractor-trailer was simulated using fuzzy logic and genetic algorithms. Operators drive the tractor-trailer back and forth several times for backing up to the loading duck. As the operators did it, a backward controller was designed using fuzzy logic. And genetic algorithms was applied to improve the performance of the backward controller. With the strings coded with the fuzzy membership functions, genetic operations were carried out. After 30 generations, the best fitted fuzzy membership functions were found. Those membership functions were used in the fuzzy backward controller. The fuzzy controller combined with genetic algorithms showed the better results than the fuzzy controller did alone.

• Journal of Korean Physical Therapy Science
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• v.16 no.2
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• pp.1-9
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• 2009

Background: The ability for backward walking is considered to be necessary for the neuromuscular control and maintenance of balance in daily ambulatory activity. This study aimed to determine the effect of backward walking training on the walking speed and balance control in patients with hemiplegia. Methods: Fourteen patients with hemiplegia were randomly allocated to an experimental and control groups of seven patients each. For the experimental group, we performed both conventional training and backward walking training, and conventional training only for the control group. The conventional training programs for the 2 groups were conducted for 30 min, twice a day, 5 times a week for 4 weeks, and backward walking training for the experimental group was conducted for 30 min, 3 times a week. The outcomes were assessed using the functional reach test (FRT), timed up-and-go (TUG) Test, and the 10 meter walk time test (10mWT). Result: A comparison of the FRT, TUG test, and 10mWT scores obtained before and after the 4-week treatment revealed statistically significant differences (p<.05) for the experimental group; however, there was no such difference in the case of the control group (p>.05). On assessment after the 4-week treatment, statistically significant differences were noted in the TUG test and 10mWT scores of the experimental group (p<.05). Conclusion: Our findings suggest that backward walking training is an effective clinical strategy for improving the walking speed and functional mobility of patients with hemiplegia.

• Journal of information and communication convergence engineering
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• v.7 no.4
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• pp.521-524
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• 2009

Park proposed a forward & backward Secure key management scheme in wireless sensor networks for Process Control Systems (PCSs) or Supervisory Control and Data Acquisition (SCADA) systems [7]. The scheme, however, is still vulnerable to an attack called "sandwich attack": two nodes captured at times $t_1$ and $t_2$, respectively, surrenders all the group keys used between times $t_1$ and $t_2$. In this paper, we propose a fix to the scheme, which can limit the vulnerable time duration to an arbitrarily chosen time span while keeping the forward and backward secrecy of the scheme untouched.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.2
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• pp.21-31
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• 2017

PURPOSE: The purpose of this study was to identify whether backward walking exercise was more effective than conventional physical therapy for balance and gait in hemiplegic stroke patients. METHODS: Eighteen patients with chronic stroke were randomly assigned to the experimental (n=9) or control (n=9) group. The experimental and control group performed backward walking exercise and conventional physical therapy, respectively, for 8 weeks. Stability Index (SI) and Weight Distribution Index (WDI) during standing were assessed using the Tetrax Balance System. The Timed Up and Go (TUG) test and Korean version of the Berg Balance Scale (K-BBS) were used to evaluate balance and fall risk. Walking speed, stride length, and step length on the affected side were measured using the 10-Meter Walk and ink foot printing tests. Wilcoxon signed-rank and Mann-Whitney U tests were used for within- and between- group comparisons, respectively. RESULTS: The experimental group showed significantly higher changes in SI (p<.01), WDI (p<.01), TUG (p<.001), and BBS score (p<.001) following intervention compared with the control group. The experimental group also showed significantly greater improvements in walking speed (p<.01), stride length (p<.001), and step length on the affected side (p<.001) after intervention compared with the control group. CONCLUSION: Backward walking exercise is an effective intervention to improve balance and gait in hemiplegic stroke patients.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.11
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• pp.984-990
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• 2002

We propose a new type of nonlinear fixed interval smoother to which an existing nonlinear smoother is modified. The nonlinear smoother is derived from two-filter formulas. For the backward filter. the propagation and the update equation of error states are derived. In particular, the modified update equation of the backward filter uses the estimated error terms from the forward filter. Data fusion algorithm, which combines the forward filter result and the backward filter result, is altered into the compatible form with the new type of the backward filter. The proposed algorithm is more efficient than the existing one because propagation in backward filter is very simple from the implementation point of view. We apply the proposed nonlinear smoothing algorithm to off-line navigation system and show the proposed algorithm estimates position, and altitude fairly well through the computer simulation.