Koki Suzuki

A car transportation system using multiple mobile robots: iCART II

This paper proposes a new car transportation system, iCART II (intelligent Cooperative Autonomous Robot Transporters - type II), based on “a-robot-for-a-wheel” concept. A prototype system, MRWheel (a Mobile Robot for a Wheel), is designed and downsized less than the half of the conventional robot used in iCART (intelligent Cooperative Autonomous Robot Transporters). In general, it is very difficult for mobile robots such as MRWheel to move to desired positions without motion errors caused by slipping, etc. Therefore we propose a decentralized control algorithm for car transportation in coordination by using a leader-follower type multiple robot system. The proposed algorithm enables the followers to estimate and reduce the motion errors and then enables the robots to transport a car to a desired position, even if the motion errors occur. In addition, we discuss how the external force applied to each robot during transporting a car, such as an inertial and friction force, is shared among the robots, and we propose a model-based external force estimation and compensation method. The proposed control algorithm is applied to the system, and the results of car transportation experiment confirm its validity.

Car transportation system grasping two drive wheels

This article describes the concept of a novel car transportation system including two mobile robots with a lift mechanism for single wheel. The system lifts only two drive wheels of a front-wheel-drive vehicle or a rear-wheel-drive vehicle, and transports them. However, the system has nonholonomic constraints because all wheels of a vehicle are not lifted by the system. This article also describes a motion control method and a vehicles wheelbase estimate algorithm for the proposed system in order to maneuver the vehicle. The motion control method is based on control theory for a three-wheeled cycle system. On the other hand, the vehicles wheelbase estimate algorithm includes impedance control, and the system estimates the vehicles wheelbase from constraint forces during transporting the vehicle. Finally, two experiments show that the proposed system can maneuver the vehicle.

Trajectory Generation for Multiple Robots of a Car Transportation System

We propose a car transportation system referred to as iCART (intelligent Cooperative Autonomous Robot Transporters). In this system, two robots approach the car autonomously, and lift up it for supporting its weight from right/left side respectively. Then, two robots transport the car in coordination. Collision-free trajectories for approaching and transporting the car are generated based on the potential field in the configuration space. In this paper, we describe details of the way to construct a configuration space, to apply a potential to the configuration space, and to generate a trajectory. Additionally, for generating the collision-free trajectory on the environment where two robots exist, repulsive potentials are applied to each robot. Described methods are integrated to iCART and experimental results illustrate the validity of the proposed method.

Cooperative transportation control in consideration of not only internal force but also external force applied to “MRWheel”

This paper proposes a new cooperative transportation control algorithm in consideration of not only the internal force but the external force applied to “Mobile Robot for a Wheel (MRWheel)”. First, we describe the merits and demerits of the model-based external force compensation method proposed in our previous study and explain the necessity of this new control algorithm. Secondly, we explain this new control algorithm mathematically. In this new algorithm, each follower receives the motion errors estimated by the other followers with TCP/IP, which enables each follower to estimate its motion error by using the force applied to it. Moreover, this new algorithm also enables “intelligent Cooperative Autonomous Robot Transporters-type II (iCART II)” to transport many types of cars at a variety of places without the preliminary car transportation needed for identifying the model parameters of the external force. Finally, we conduct the transportation experiments of two types of cars for the comparison between this new algorithm and the conventional algorithm with the modelbased external force compensation method. These experimental results illustrate the validity of this new control algorithm.

A COOPERATIVE TRANSPORTATION SYSTEM OF A CAR WITH MULTIPLE MOBILE ROBOTS: ICART II

In this paper, a new car transportation system and a prototype robot that are based on the “a-robot-for-a-wheel” concept are introduced. In addition, a decentralized control algorithm for cooperative car transportation using a leader–follower type of multiple robot system is proposed. An external force compensation method is explained for extracting only internal force from the force applied to the robots. The proposed algorithm is experimentally validated by application to a car transportation system. Finally, the application of the proposed system to medical and welfare mobile apparatuses is described.