Woojin Chung

Design and control of the nonholonomic manipulator

Nonholonomic constraints are exploited to design a controllable n-joint manipulator with only two inputs. Gears subject to nonholonomic constraints are designed to transmit velocities from the inputs to the passive joints. The system possesses a triangular structure for which a conversion into chained form is presented. The nonholonomic manipulator can, therefore, be controlled with an open loop or a closed loop using existing controllers for chained form. Mechanical design is established, and experimental results proved the usefulness of design of the nonholonomic manipulator and applied control schemes. While previous publications have assumed that the nonholonomic systems are given and have developed theory for these systems, this paper points out a new direction where the nonholonomic theory is used to design controllable and stabilizable systems.

Discrete-Status-Based Localization for Indoor Service Robots

This paper proposes a new localization strategy for indoor service robots. A mobile robot localization problem is difficult to solve by a single continuous algorithm. Major difficulties include dynamic changes of the real world, various uncertainties, limitation of sensor information, and so forth. To develop a practical localization solution, this paper proposes an integrated localization strategy based on the discrete status of the mobile robot. Uncertainties of navigation are specified and classified into discrete status, and then modeled as a Petri net-based discrete localization system. The proposed algorithm integrates developed computational schemes and robot behaviors with respect to the defined status. Major criteria of status discretization include geometric properties of the environment, existence of dynamic obstacles, and reliability level of the estimated position. An efficient map-matching scheme and a map-building strategy are developed toward practical implementations. This paper focuses on providing a synthesized practical localization method, which can deal with various uncertainties by explicit discretization of robot status. The feasibility of the proposed method is experimentally verified with prototype public service robots in dynamic real environments

Design of a nonholonomic manipulator

Nonholonomic systems are typically controllable in a configuration space of higher dimension than the input space. Here, it is shown how nonholonomic constraints can be exploited to design a controllable n-joint manipulator with only two inputs. Gears subject to nonholonomic constraints are designed to transmit velocities from the inputs to the unactuated joints. The designed nonholonomic manipulator is shown to be completely controllable in the whole configuration space. The system is designed with a triangular structure for which a conversion into chained form is presented. The nonholonomic manipulator can, therefore, be controlled using existing controllers for chained form.<<ETX>>

Door opening control using the multi-fingered robotic hand for the indoor service robot

KIST service robot is composed of a mobile platform, a 6 DOF robotic manipulator, and a multi-fingered robotic hand. We discuss motion control and coordination strategy in order to deal with uncertainty problem in practical applications. A door opening is our target task. Since the environment is not prepared for a service robot, it is essential to deal with various uncertainties due to a robot positioning error, sensing error, as well as manipulation errors. In this paper, practical parameter estimation schemes are proposed from the viewpoint of coordinative motion control of a hand, a manipulator and a mobile robot. Analysis of physical properties of each component provides a methodology of appropriate role assignment for each component. In order to carrying out compliance control, an external force is computed using fingertip force information of the three fingered robot hand, instead of using force torque sensor at the wrist. Presented experimental result clearly shows the effectiveness of the proposed scheme.

The autonomous tour-guide robot Jinny

This paper explains a new tour-guide robot Jinny. The Jinny is developed by focusing on human robot interaction and autonomous navigation. In order to achieve reliable and safe navigation performance, an integrated navigation strategy is established based on the analysis of a robots states and the decision making process of robot behaviors. According to the condition of environments, the robot can select its motion algorithm among four types of navigation strategy. Also, we emphasized the manageability of a robots knowledge base for human friendly interactions. The robots knowledge base can be extended or modified intuitively enough to be managed by non-experts. In order to show the feasibility and effectiveness of our system, we also present experimental results of the navigation system and some experiences on practical installations.

Control of a mobile robot with passive multiple trailers

A mobile service robot can achieve reconfigurability by exploiting passive trailer systems. Reconfigurability provides significant practical advantages in order to deal with various service tasks. However, a motion control problem of a passive multiple trailer system is difficult, mainly because a kinematic model is highly nonlinear. It is shown how a robot with n passive trailers can be controlled in backward direction. Once a desired trajectory of a last trailer is computed, then the control input of a pushing robot is obtained by the proposed control scheme. A kinematic design of a trailer system is proposed in our prior work. It is shown that the high performance of trajectory tracking is also valid for the backward motion control problem. Experimental verifications were carried out with the PSR-2 (public service robot) with three passive trailers. Experimental result showed that the backward motion control could be successfully carried out using the proposed control scheme.

Tripodal schematic design of the control architecture for the Service Robot PSR

This paper describes a control architecture design and a system integration strategy for the autonomous service robot PSR (Public Service Robot). The PSR is under development at the KIST (Korea Institute of Science and Technology) for service tasks in public spaces such as office buildings and hospitals. The proposed control architecture is designed by tripodal frameworks, which are layered functionality diagram, class diagram, and configuration diagram. The tripodal schematic design clearly points out the way of integrating various hardware and software components. The developed strategy is implemented on the PSR and successfully tested.

A reliable position estimation method of the service robot by map matching

In this paper, a reliable position estimation method of the indoor service robot is proposed. The service robot PSR1 is a wheeled mobile manipulator which navigates in office buildings. Our localization method is a map-matching scheme using scanned range data, without using any artificial landmark. The proposed algorithm can provide solutions for both a global localization problem and a local position tracking. A probabilistic position estimation scheme is designed based on MCL (Monte Carlo localization). Two measure functions are developed for computing positional probabilities. The robot automatically decides whether it uses geometric pattern matching (i.e. walls, pillars) by Hough transform. The proposed scheme shows reliable performance in both polygonal environments and non-polygonal environments even there exist many obstacles. Experimental results demonstrate the validity and feasibility of the proposed localization algorithm for the service robot to navigate in an office building, using the natural environmental characteristics.

Tripodal Schematic Control Architecture for Integration of Multi-Functional Indoor Service Robots

This paper discusses a control architecture and a system integration strategy for multifunctional indoor service robot public service robot (PSR) systems. The authors have built three versions of the PSR systems for four target service tasks, which are delivery, patrol, guidance, and floor cleaning. They clarify the requirements of the architecture in their applications, and propose the tripodal schematic control architecture as the solution to the architectural problems. The key idea of proposed architecture is to integrate robot systems using following three frameworks, layered functionality diagram, class diagram, and configuration diagram. The proposed architecture was successfully evaluated and implemented to PSR platforms for their target tasks. Experimental results clearly showed that the developed strategy was useful for developing the autonomous service robots

A passive multiple trailer system for indoor service robots

It is shown how a passive multiple trailer system is designed and controlled for practical applications. The main focus is reducing the trajectory tracking error and the scope of the paper is limited to the passive systems due to the cost and simplicity of the trailer mechanism. Three kinds of passive trailers are introduced, and then the analysis of path tracking performance is carried out, in order to show that the proposed off-hooked trailer is advantageous in a practical sense. Stability, issues are discussed with constant reference velocity. Numerical simulation results and experimental results are presented.