Riadh Zaier

Piecewise-Linear Pattern Generator and Reflex System for Humanoid Robots

Reflexes have been viewed as integrated motions with the centrally generated motors commands to produce adaptive movement. In this paper, a walking pattern generator for humanoid robots based on piecewise linear functions and inspired by passive walking is considered. To deal with lateral and frontal disturbances, sensory feedback is realized based on the inverse pendulum model. The reflex system that highly adapts and controls the movement of the humanoid robot, when a large disturbance occurs, is combined with the motion pattern generator and proposed in a unified form with regards to three types of sudden events. Experiments using Fujitsus humanoid robot HOAP-3 demonstrate that a reflex movement is successfully integrated with the rhythmic motion when there are sudden changes in floor level, when obstacles suddenly appear, and in the presence of a large disturbance. The proposed reflex system therefore contributes toward the safe interaction of humanoid robots with the environment.

Motion Pattern Generator and Reflex System for Humanoid Robots

Reflexes have been viewed as an integrated motion with the centrally generated motors commands to produce adaptive movement. In this paper, the reflexes that highly adapt and control the movement of the humanoid robot when a large disturbance occurs is considered. The structure of the reflex system is proposed combined with the walking motion generator. Our approach to generate a rhythmic motion does not require complex dynamics models. It is based on linear oscillators and provides flexibility in introducing reflexes. In order to demonstrate the effectiveness of the proposed system, the humanoid robot HOAP-3 of Fujitsu is used. It is shown that a reflex movement is successfully integrated with the rhythmic motion in the following case; sudden change in the floor level, sudden change in load, and presence of a large disturbance. As a result, the proposed reflex system contributes toward the safe interaction of the humanoid robots with the environment

Adaptive locomotion controller and reflex system for humanoid robots

This paper deals with reflexes against sudden obstacles for humanoid robots, which are combined with a proposed piecewise-linear pattern generator. The reflex action consists of modulating the motorspsila commands by the outputs of the force sensors located under the robot legs, and through a given primitive neural network previously proposed. Eventually, the primitive reflex is modified by the afferent signals to be more adaptable and robust against sudden obstacles. The final reflex structure enables the response of the sensory signals to be coordinated and modulated with locomotion controllerpsilas outputs to achieve an intended stabilizing behavior of the robot. The effectiveness of the proposed reflex is demonstrated by experiment using Fujitsupsilas humanoid robot HOAP-3. It is shown that the primitive reflex movement previously proposed becomes robust against sudden obstacle that hits the robot sole plate at different locations. The proposed reflex system, therefore, contributes towards the safer interaction of the humanoid robot with the environment.

Legged Vehicle Control and Vibration Reduction

This paper presents a design method of controller reducing the vibration of the upper body of a legged vehicle during locomotion. To design locomotion pattern generator, instead of using non-linear dynamics models and solving complex equations, the control strategy is simply based on the use of piecewise linear oscillators and a few parameters that can be easily obtained and tuned. In this research framework, we present tuning algorithms of both the rolling profile and the feedback controllers gains such that the mechanical vibration in the legged vehicle during locomotion is attenuated. As a result, stable and smooth locomotion is obtained. The effectiveness of the proposed method is demonstrated by experimental results.

Design and implementation of smart irrigation system for groundwater use at farm scale

Recently there has been an excessive groundwater pumping and seawater intrusion in the costal aquifers of Oman. To deal with this problem, a fully automated and wireless irrigation control system that avoids subjective decisions about irrigation volumes and timing was developed. All fields in the farm are accessible via TCP/IP protocol. Each farm has a Single Collecting Node for data collection connected to a host computer. All nodes in a crop are connected to Xbee network and considered as Slave Nodes except one termed Master Node. The Master Node includes two sensors and a solenoid valve. The Master Node controls the irrigation of the field with a same crop sequentially using slave nodes. Both the Xbee network and the solenoid valves are powered by a lithium battery with photovoltaic charging panels. The irrigation control and monitoring program is implemented in the host computer in the farm, which monitors the states of all crops and controls the valves using a threshold and timers. The smart irrigation system has been installed in 14 farms.

Design of locomotion controller and reflex for humanoid robot

Designing a network of oscillators that controls the locomotion of a legged robot can be thought as a complex problem hard to solve. This paper, therefore, attempts towards simplifying the design method of the locomotion controller by combining a linear piece wise liner oscillator (PWL) and the Van der Pol oscillator (VDP). The VDP oscillator will be considered as a master oscillator as it will generate the rolling motion pattern. The pitching and swing motion will be generated by the PWL. The selection of the oscillator type is made based on our previous result on motion pattern generator using piecewise linear functions. The VDP oscillator is selected to have a stable limit cycle close to the one obtained in our previous results. The robustness of the locomotion controller will be analyzed by introducing a small perturbation to the oscillators equation. By changing randomly the perturbation parameter within limited interval results into a “fluid motion” of the robot. In addition, the locomotion controller will be designed as a neural network that will be coupled to the robot dynamics through sensory system containing proportional derivative controllers to exhibit natural looking motion.

Control of biped robot joints' angles using coordinated matsuoka oscillators

Neural Oscillators are network of neurons that produce smooth oscillatory/rhythmic pattern. In this paper, a simple network of Matsuoka oscillators is used to generate the bipedal locomotion by coordinating the joint angle using a new method of coordination proposed by Huang. This method makes the control of the joint angle easier as they are related with each other in a sequential manner. Also, this method prevents error accumulation with time. The results show that the robot produced a smooth walking motion.

Hard Disk Drive Manufacturing Optimization

Rapid increase in demand for high hard disk data storage density is forcing R&D centers and manufacturing companies to focus on continuous improvement of hard disk drive (HDD) performance. Current HDD records data on the magnetic disk or platter by controlling a magnetizing ferromagnetic material directionally. The data are read from the disk using a magnetic head by detecting the transitions in magnetization and decoding the originally written data pattern. To extract the best performance from these improved materials, manufacturing process, and design of platter and magnetic head, this article proposes a real time control method for the magnetic head by controlling the arm actuator. This can guarantee fast and accurate positioning performance and larger storage capacity. The control algorithm is based on a modified simplex method and can be implemented online and run in real-time control.

A novel pin-on-disk machine for stick-slip measurements

A novel pin-on-disk machine is designed and constructed to provide the facility of vibrating the test samples at different amplitudes and frequencies of vibration in order to examine their effects on stick-slip amplitudes. The machine is equipped with control features and sensors with an integrated data acquisition system to regulate normal applied load and relative spindle speed. This machine is used as pin-on-disk type with the option of changing the sample jig and fixture. Friction stability of different types of soft and hard materials is investigated by means of variation of stick-slip amplitude with amplitude of normal vibration when mild steel pin slides on mild steel, glass fiber reinforced plastic (GFRP), polytetrafluoroethylene (PTFE), and rubber. Proper construction of the machine was validated by comparing the friction coefficients for tests performed on the machine with published results using similar machine. The results revealed that within the observed range the stick-slip amplitude depends on the material type and stick-slip amplitude decreases with the increase of amplitude of vibration. The rate of stick-slip amplitude reduction has a particular relationship with material, amplitude and frequency of vibration.