Jin-Geol Kim

Stability experiment of a biped walking robot with inverted pendulum

This paper is concerned with a balancing motion formulation and control of the ZMP (zero moment point) for a biped walking robot that has a balancing weight of an inverted pendulum. The original dynamic stability equation of a walking robot is nonlinear; because its balancing weight is an inverted pendulum type. The stabilization equation of a biped walking robot is modeled as a linearized non-homogeneous second order differential equation with boundary conditions. With the FDM (finite difference method) solution of the linearized differential equation, a trajectory of balancing weight can be directly calculated. Furthermore, it makes that possible input the desired ZMP or ZMP trajectory for various gait, situation and complex motion. Also, it can be easily approximated that a balancing range or motion when some link parameters are changed; especially a balancing mass is changed. In this paper, the simulator with a balancing weight of an inverted pendulum is programmed to get and calculate the desired ZMP and the actual ZMP. The operating program is developed for a real biped walking robot IWRIII-IP. Walking of 6 steps will be simulated and experimented with a real biped walking robot. This balancing system will be applied to a biped humanoid robot, which consist legs and upper body, at future work.

Optimal walking trajectory generation for a biped robot using genetic algorithm

Information of suitable additive via-points, which determine the shapes of trajectories, such as velocities and accelerations at the via-points, are needed for smooth biped walking. Also, incorrect information can cause indifferentiability on the trajectory and result in discontinuous walking motion. In the paper optimal via-points data are found using a genetic algorithm which minimizes the sum of deviation of velocities and accelerations as well as a jerk. As a result, we obtain the continuity on the whole trajectory interval, the energy distribution through optimum velocities and accelerations. Smooth and stable walking with the leg trajectory optimized by genetic algorithm is shown by walking experiments.

Backlash compensation for a humanoid robot using disturbance observer

This paper describes the control of a geared DC motor having a backlash for implementation of a humanoid robot using disturbance observer. Critical problem of the humanoid robot is caused by the nonlinearity such as a backlash. To meet this problem, a control method using disturbance observer has been proposed. The disturbance observer is designed to estimate the effects of nonlinearities in the system, to make the nonlinear system behave linearly, and to cancel them efficiently. To design the low-pass filter in the disturbance observer, cut-off frequency of the output should be found. The goal of this paper is the implementation of the proposed system, compensating the backlash effect. To accomplish the goal, PD control and disturbance observer are employed to the system with no load and full load. As a result, system stability can be guaranteed by compensating the effect of backlash. In addition, real experiment shows the proposed control methodology will satisfy the stable working of a humanoid type in the future.

Messages scheduling for a humanoid robot in the CAN

This paper deals with the messages scheduling of a CAN (Controller Area Network), based on the distributed control scheme to integrate actuators and sensors in a humanoid robot. In order to supply the distributed processing for a humanoid robot, each control unit should have the efficient control method, fast calculation and valid data exchange. The preliminary study has concluded that the performance of CAN is better and easier to implement than other network such as FIP (Factory Instrumentation Protocol), VAN (Vehicle Area Network), etc. Since a humanoid robot has to treat the significant control signals from many actuators and sensors, the communication time limitation could be critical according to the transmission speed and data length of CAN specification. In this paper, the CAN message scheduling in a humanoid robot was suggested under the presence of Jitter in the message group, the existence of high load of messages over the network and the presence of transmission errors. In addition, the response time under the worst case is compared with the limitation by using the simulation algorithm. As a result, the suggested messages scheduling can guarantee our CAN limitation, and utilize to generate the walking patterns for the humanoid.

Adaptive gait algorithm for IWR biped robot

This paper is concerned with the ZMP (zero moment point) control algorithm for the IWR biped walking robot, which is under development in Korea. The authors introduce a ZMP control method of dynamic biped walking with a special trunk mechanism. The trunk is for balancing during walking, which requires a small balancing space in motion. Walking simulations with the IWR model are shown using the proposed ZMP control method. As a result, the various gaits generation for adapting to the different environments and system stabilization with complex trajectories of swing-leg and support-leg are presented.<<ETX>>

Robust control for dynamic walking of a biped robot with ground contacting condition

A robust controller with the sliding mode is proposed for stable dynamic walking of a biped robot in this paper. The robot system is modeled as 14-DOF rigid bodies considering kinematic construction of a humanoid. The method of multibody dynamics is applied to construct the equations of motion for the complicated biped robot system. In order to obtain the optimized trunk trajectory, the modified FFT method is solved iteratively. The dynamic walking simulation is performed by using optimized trajectories of the trunk and each foot. Also, Hertz force model and hysteresis damping element are employed for the ground reaction and impact forces during contact with the ground. Finally, the sliding mode control is applied to solve the problems of modeling imprecisions or uncertainties. Under the assumption of the bounded estimation errors on the unknown parameters, the proposed controller provides a successful way to achieve the stability and good performance.

A Study on the Joint Controller for a Humanoid Robot based on Genetic Algorithm

This paper presents a joint controller for a humanoid robot based on genetic algorithm. h humanoid robot has basically instability during walking because it isn`t fixed on the ground. Moreover nonlinearities of the joints increase its instability. If one of them isn`t satisfied, the robot may fall down at the ground during walking. To attack one of those problems, joint controller is proposed. It can perform tracking control preciously and reduce the effect of nonlinearities by gear, limitation of the input voltage, coulomb friction and so on. This controller is based on fuzzy-sliding mode controller (FSMC) and compensator and control gains are searched by a proposed genetic algorithm. It can reduce the effect by nonlinearities. Also, to improve the tracking performance, the proposed controller has motion controller. From the given controller, a humanoid robot can moved more preciously. Here, all the processes are investigated through simulations and it is verified experimentally in a real joint system for a humanoid robot.

Nonlinear motor control using dual feedback controller

This paper is concerned with the control of multiple nonlinearities included in a humanoid robot system. A humanoid robot has some problems of the structural instability basically, which leads to consider the control of multiple nonlinearities caused by driver parts as well as gear reducer. Saturation and backlash are typical examples of nonlinearities in the system. The conventional algorithms of backlash control are based on fuzzy algorithm, disturbance observer and neural network, etc. However, it is not easy to control the system that is employed by only single algorithm because the system includes multiple nonlinearities. In this paper, a switching PID is considered for a control of saturation, and a dual feedback algorithm is proposed for a backlash control. To implement the above algorithms, the system identification is firstly performed for the minimization of the difference between simulation and experiment. After that, the switching PID gains are determined using genetic algorithm for removing limit cycle by saturation. The control algorithm is applied by dual feedback concept based on disturbance observer. All the processes are investigated through simulations and are verified experimentally in a real humanoid system.

Design of a switching PID controller using advanced genetic algorithm for a nonlinear system

This paper deals with a switching PID controller using a genetic algorithm in a multi-nonlinear system. In controlling the nonlinear element of the system, there are some problems such as the limit cycle. In this study, a switching PID controller was proposed to solve problems caused by nonlinearities of system. The PID is a well-known robust controller. But, in a motor system case, it may have a limit cycle when proportional gains exceed limit. However, in other case, if the PID gain is relatively small, its torque characteristics can be too weak. In this case, the suggested switching PID controller was found to be a good approach for solving these problems despite there being difficulties in determining its boundary and gains at each boundary. In this paper, an improved genetic algorithm was used for identifying a motor system and to determining each gain for the controller. In particular, new type of crossover and mutation using a sigmoid function is applied to improve the searching ability based on the proposed improved genetic algorithm. All the processes are investigated through simulations and are verified experimentally in a real motor system.

H Design of Decoupled Control Systems Based on Directional Interpolations

H design of decoupled control systems is treated in the generalized plant model. The existence condition of a decoupling controller is stated and a parameterized form of all achievable decoupled closed loop transfer matrices is presented by using the directional interpolation approaches under the assumption of simple transmission zeros. The class of all decoupling controllers that yield finite cost function is obtained as a parameterized form and an illustrative example to find the optimal controller is provided.