Chang-Soon Hwang

Wearable haptic-based multi-modal teleoperation of field mobile manipulator for explosive ordnance disposal

This paper describes a wearable multi-modal user interface design and its implementation for a teleoperated field robot system. Recently some teleoperated field robots are employed for hazard environment applications (e.g. rescue, explosive ordnance disposal, security). To complete these missions in outdoor environment, the robot system must have appropriate functions, accuracy and reliability. However, the more functions it has, the more difficulties occur in operation of the functions. To cope up with this problem, an effective user interface should be developed. Furthermore, the user interface is needed to be wearable for portability and prompt action. This research starts at the question: how to teleoperate the complicated slave robot easily. The main challenge is to make a simple and intuitive user interface with a wearable shape and size. This research provides multi-modalities such as visual, auditory and haptic sense. It enables an operator to control every functions of a field robot more intuitively. As a result, an EOD (explosive ordnance disposal) demonstration is conducted to verify the validity of the proposed wearable multi-modal user interface.

Mobile Robot for Door Opening in a House

A new field of robot applications is emerging. Owing to the relevancy of the robot, people’s convenience can be enhanced. In this paper, we study on the task of opening a closed door by the home service robot which is mobile robot equipped with a manipulator. The objective of this research is to successfully accomplish door opening task using the home service robot. In addition, the robot has some advantages as the home service robot for the general use. The proposed robot is small and compact because double active universal joint is adopted for the robotics joint mechanism of the manipulator so it easy to move in a house through doorways. Moreover, cheap force sensors are employed for the information of door opening task instead of expensive JR3 sensor so we can expect cost effectiveness in the robot. Practical experiment has shown that the door opening task can be completed successfully by the proposed home service robot which is small, compact, inexpensive but efficient.

Energy-based control of a passive haptic device

We propose an energy-based control method of a passive haptic device equipped with electric brakes. Unstable behavior is observed in the passive haptic system due to time delay mainly arising from the slow update rate of the virtual environment. From the passive FME (force manipulability ellipsoid) analysis, a so-called direct force control method is proposed in this paper. Its gain is computed by force analysis at the end-effector of a passive haptic device so that the component of a resultant force at the end-effector causing a pullback motion becomes zero. However, this direct force control scheme requires precise measurement of the hand force input by a human operator. We also propose the indirect force control scheme in which the gain in the direct force control scheme is computed using the notion of passivity without resorting to the high precision force sensor. For the experiments a 2-link passive haptic system was developed in this research. Various experiments have been conducted to investigate the validity of both direct and indirect force control schemes proposed in this paper. It is shown that both schemes produce satisfactory performance in the force display for the wall-following task on the virtual wall.

Control program of two-fingered dexterous manipulation with primitive motions

This paper presents a motion planning and control method for the dexterous manipulation with a robotic hand. For a given trajectory of an object, a simulation system calculates the necessary joint displacements and contact forces at the fingertips. These joint displacements and contact forces are the reference inputs to the control loops of the robotic fingers. A task is decomposed into a set of primitive motions, and each primitive motion is executed using the output of the simulation system as the reference. Force sensors and dynamic tactile sensors are used to adapt to uncertainties encountered during manipulation. Several experimental results are presented.

Teleloperation of field mobile manipulator with wearable haptic-based multi-modal user interface and its application to explosive ordnance disposal

This paper describes a wearable multi-modal user interface design and its implementation for a teleoperated field robot system. Recently some teleoperated field robots are employed for hazard environment applications (e.g. rescue, explosive ordnance disposal, security). To complete these missions in outdoor environment, the robot system must have appropriate functions, accuracy and reliability. However, the more functions it has, the more difficulties occur in operation of the functions. To cope up with this problem, an effective user interface should be developed. Furthermore, the user interface is needed to be wearable for portability and prompt action. This research starts at the question: how to teleoperate the complicated slave robot easily. The main challenge is to make a simple and intuitive user interface with a wearable shape and size. This research provides multi-modalities such as visual, auditory and haptic sense. It enables an operator to control every functions of a field robot more intuitively. As a result, an EOD (explosive ordnance disposal) demonstration is conducted to verify the validity of the proposed wearable multi-modal user interface.

Evaluation of robotic fingers based on kinematic analysis

This paper presents an evaluation of joint configurations of a robotic finger based on kinematic analysis. The evaluation is based on an assumption that the current control methods for the fingers require that the contact state specified by the motion planner be maintained during manipulation. Various finger-joint configurations have been evaluated for different contact motions. In the kinematic analysis, the surface of the manipulated object was represented by B-spline surface and the surface of the finger was represented by cylinders and a half ellipsoid. Three types of contact motion, namely: 1) pure rolling, 2) twist-rolling, and 3) slide-twist-rolling are assumed in this analysis. The finger-joint configuration best suited for manipulative motion is determined by the dimension of manipulation workspace. The evaluation has shown that the human-like fingers are suitable for maintaining twist-rolling and slide-twist-rolling but not for pure rolling. A finger with roll joint at its fingertip link, which is different from human fingers, proved to be better for pure rolling motion because it can accommodate sideway motions of the object. Several kinds of useful finger-joint configurations suited for manipulating objects by fingertip surface are proposed.

Passivity control of a passive haptic device

In this paper, we propose an energy-based stability control of a passive haptic device equipped with passive actuators such as an electric brake. Unstable behavior is observed even in the passive haptic system due to time delay mainly arising from the slow update rate of the virtual environment. The force approximation, one of the major limitations of the passive haptic device, is explained in the passive FME analysis. The ideal force display of passive haptic device is investigated, and it is shown that the passive haptic system frequently obtains the pullback capability due to the force approximation. The indirect force control scheme is proposed in that the change rate of passivity is controlled to simulate the ideal force display. To avoid the increase of the passivity due to the rate controller, which is not correlative to stability, passivity feedback is established. An experiment was conducted with a 2-link passive haptic device equipped with two electric brakes. From the experiment, the proposed control method showed satisfactory performance in displaying a plain virtual wall.