Issam A. Smadi

Development, Analysis, and Experimental Realization of a Direct-Drive Helical Motor

Safety issue is a great concern for rehabilitation robots that are expected to contribute to future aging society. Appropriate compliance is required for their joints. However, combination of servomotors and high-ratio gears, such as harmonic gears, makes the joint of robots nonbackdrivable. The nonbackdrivability causes lack of adaptability and safety. On the other hand, conventional direct-drive systems, including linear motors, are relatively big for such application. This paper presents the development and analysis of compact high-backdrivable direct-drive linear actuator. The motor consists of a helical structure stator and mover. The mover does not contact the stator and moves helically in the stator under a proper magnetic levitation control. Thus, the motor realizes direct-drive motion without mechanical gears. Decoupling control is proposed and integrated with disturbance observer to achieve robustness against model uncertainties and input disturbance. The main contribution of this paper is to experimentally realize the direct-drive feature of the helical motor.

Modeling and control of a high-thrust direct-drive spiral motor

In this paper, modeling and control of spiral motor is proposed. The voltage equation and motion equation of the spiral motor is proposed. Based on this modeling, control system for the spiral motor is proposed. The proposed controller consists of three parts; the first part is PI current controller with back EMF compensation specialized for spiral motor, the second part is disturbance observer based PD controller for linear and gap motion interacting each other, and the third part is zero-power controller for equilibrium fluctuation of gap displacement. It is confirmed that the proposed controller achieves independent linear position and gap control simultaneously.

Fuzzy logic controller for overhead cranes

Purpose – To propose a new method for controlling the overhead crane systems based on the theory of fuzzy logic with a reduced number of rules than has appeared before in the literature. The proposed fuzzy logic controller (FLC) can be implemented to move the overhead crane along a desired path while ensuring that the payload is swing free at the end of the motion.Design/methodology/approach – In this study, a FLC that includes two rule bases, one for displacement control, the other for swing control, was designed and successfully implemented to move the overhead crane along a desired path while ensuring that the payload is swing free at the end of the motion.Findings – Control simulation results demonstrate that by using the proposed FLC, the overhead traveling crane smoothly moves to the destination in short time with small swing angle and almost no overshoot.Originality/value – This paper offers practical help to whom are working in controlling the transporting the payloads to the required position as ...

On Fuzzy Control of Chaotic Systems

In this paper, we introduce the control of the strange attractor, chaos. Because of the importance of controlling undesirable behavior in systems. researchers are investigating the use of linear and nonlinear controllers, either to remove such oscillations (in power systems) or to match two chaotic systems (in secure communications). The idea of using the fuzzy logic concept for controlling chaotic behavior is presented. There are two good reasons for using fulzy control: first, there is no mathematical model available for the process; secondly. it can satisfy nonlinear control that can be developed empirically. without complicated mathematics. The two systems are well-known models so the first reason is not a big problem. and we can take advantage of the second reason.

On a high-backdrivable direct-drive actuator for musculoskeletal bipedal robots

This paper reports on newly developed small-size prototypes of spiral motors for a musculoskeletal robot application. The prototype has smooth helical surface so that the mover can touch down the stator. The stator core is made from SMC (Soft Magnetic Composite) in order to reduce iron loss. Helical-shape permanent magnets are mounted on the surface of the mover. The motor realizes compact direct-drive motion systems. A concept and design sketch of a musculoskeletal robot in which the spiral motors are installed as artificial muscle is shown. Also modeling and control of the spiral motor are reported.

On independent position/gap control of a spiral motor

This paper presents a full direct-drive motion of a spiral motor. Spiral motor, is a novel high thrust force actuator with high backdrivability, consists of a spiral structure mover and stator. The mover moves spirally in the stator, and the linear motion is extracted to drive the load. A proper gap control against the load fluctuation is needed to achieve full direct drive motion. In this paper, an exact feedback linearization engaged with DOB is used to achieve independent position/gap control of a spiral motor. Through the use of high gain feedback time scale separation is artificially introduced and the overall closed-loop system is transformed into a singular perturbation one. Then, using tools from singular perturbation theory, the proposed method ensures arbitrary disturbance attenuation, small tracking error, and boundness of all closed loop signals. Finally, simulation results are given to verify the theoretical one.

Development of musculoskeletal biped robot driven by direct-drive actuators

We develop a new musculoskeletal biped robot driven by bigh-thrust direct-drive linear actuator; spiral motor. The motor is compact even though it is not combined with mechanical gears. Thanks to its gearless mechanism, fine position/force control is possible. Direct-drive position control is verified by experiments, where very quick motion is realized. Moreover, simulation method for musculoskeletal biped robot is proposed.

On direct-drive motion of a spiral motor

Spiral motor, a novel high-thrust linear actuator with high backdrivability, consists of a helical structure stator and mover. Under proper gap control against the load fluctuation, the mover moves helically in the stator and the linear motion is extracted to drive the load. Thus, the motor realizes direct-drive motion without mechanical gears. In this paper, an exact feedback linearization engaged with disturbance observer (DOB) is used to achieve full direct-drive motion of a spiral motor. Through the use of high gain feedback time scale separation is artificially introduced and the overall closed-loop system is transformed into a singular perturbation one. Then, using tools from singular perturbation theory, the proposed method ensures arbitrary disturbance attenuation, small tracking error, and boundness of all closed loop signals. Simulation and experimental results are given to verify the theoretical one.

A robotic cane for walking assistance

New design and control of a robotic cane have been proposed in this paper. Our robotic cane has been designed so that it moves according to users small force applied to the cane and it stably supports the user when large force is applied by the user. We confirmed our control and estimation of human force method in 2D and 3D simulation. In this paper, an overview of the design and a robust control method are presented.

Development of a biarticular manipulator using spiral motors

This paper presents the design and development of a musculoskeletal-inspired robot manipulator using the third prototype of the spiral motor developed in our laboratory. The spiral motors represents the linear contraction/extension of the antagonistic muscles due to the high forward/backward drivability without any gears or mechanisms. Workspace was evaluated and simulations were done in some control schemes to compare the probable methods of workspace control. Finally, spiral motor control and experimental results were presented.