Nazir Kamaldin

Toward Comprehensive Modeling and Large-Angle Tracking Control of a Limited-Angle Torque Actuator With Cylindrical Halbach

The single-phase limited-angle torque (LAT) motor with cylindrical Halbach magnetic array provides a smaller form factor, lighter moving mass, and higher force throughput within ±60° angle range, compared with the three-phase permanent magnet synchronous motor. Due to the imperfect flux distribution within the air-gap of the Halbach array, as well as the inherent angular dependent characteristics, it is mainly used for point-to-point motion applications in prior literature. In this paper, we would like to deal with above issues, so that it can be extensively used for large-angle tracking applications. First, we derive the ideal model of this LAT actuator. Next, we propose to identify its nominal model parameters by the relay feedback with sufficiently small oscillations near the neutral position. Later, a robust output feedback control with high-gain observer is proposed to handle both model uncertainty and angular-dependent nonlinear current-torque relationship, so that the precision tracking of a defined smooth trajectory is achieved with only position sensing. The real-time experiment on a prototype validates the practical appeal of proposed methods.

A Magnetic Resonance Compatible Soft Wearable Robotic Glove for Hand Rehabilitation and Brain Imaging

In this paper, we present the design, fabrication and evaluation of a soft wearable robotic glove, which can be used with functional Magnetic Resonance imaging (fMRI) during the hand rehabilitation and task specific training. The soft wearable robotic glove, called MR-Glove, consists of two major components: a) a set of soft pneumatic actuators and b) a glove. The soft pneumatic actuators, which are made of silicone elastomers, generate bending motion and actuate finger joints upon pressurization. The device is MR-compatible as it contains no ferromagnetic materials and operates pneumatically. Our results show that the device did not cause artifacts to fMRI images during hand rehabilitation and task-specific exercises. This study demonstrated the possibility of using fMRI and MR-compatible soft wearable robotic device to study brain activities and motor performances during hand rehabilitation, and to unravel the functional effects of rehabilitation robotics on brain stimulation.

Adaptive parameter and gain RISE control of a flexure-based dual-drive ‘H’ gantry

The dual-drive gantry has widespread industrial use. It is mechanically advantageous in terms of ease and cost of manufacture, low use of precision machined parts, power efficiency among the more significant features. However, control of the prototype gantry is not trivial. Inter-axis misalignment, manufacturing imperfections contribute to the difficulty of control. In addition to all the complexities of contemporary dualdrive gantries, our prototypes end-effector is actuated through a force with a fixed line of action. This causes a moment that de-synchronizes the motion of the parallel carriages. Furthermore, contemporary robust control schemes such as sliding mode control can excite hidden modes related to the flexure joints. An output-feedback control scheme that uses both an online parameter adaptation in conjunction with a robust integral signum of error (RISE) gain evolution is proposed. Experimental results show improvement of the proposed controller against a conventional RISE counterpart.

Integrated Mechatronic Design in the Flexure-Linked Dual-Drive Gantry by Constrained Linear–Quadratic Optimization

A dual-drive H-gantry is commonly used in many industrial processes to meet the requirement of high-precision Cartesian motion. Unlike the rigid-linked gantry stage, the flexure-linked counterpart allows a small degree of rotation of the crossarm to prevent possible damages. However, by this design, the chattering of control signals and inappropriate stiffness of the flexure may induce the resonant modes of the gantry. Hence, to maintain the precision tracking of the midpoint position and the orientation of the gantry, as well as to minimize the vibration on the end effector, we seek the most suitable flexure stiffness and controller parameters by formulating a constrained linear–quadratic optimization problem. Since such a mechatronic design problem is not solvable via standard linear–quadratic regulator formulas, we convert it to a constrained projection gradient-based optimization problem, which can be efficiently solved by direct computation of projection gradient and line search of optimal step length. A fast convergence of parameters is achieved after first several iterations. Through a series of comparative experiments, the effectiveness of the proposed method is validated.

A novel constrained H2 optimization algorithm for mechatronics design in flexure-linked biaxial gantry

The biaxial gantry is widely used in many industrial processes that require high precision Cartesian motion. The conventional rigid-link version suffers from breaking down of joints if any de-synchronization between the two carriages occurs. To prevent above potential risk, a flexure-linked biaxial gantry is designed to allow a small rotation angle of the cross-arm. Nevertheless, the chattering of control signals and inappropriate design of the flexure joint will possibly induce resonant modes of the end-effector. Thus, in this work, the design requirements in terms of tracking accuracy, biaxial synchronization, and resonant mode suppression are achieved by integrated optimization of the stiffness of flexures and PID controller parameters for a class of point-to-point reference trajectories with same dynamics but different steps. From here, an H2 optimization problem with defined constraints is formulated, and an efficient iterative solver is proposed by hybridizing direct computation of constrained projection gradient and line search of optimal step. Comparative experimental results obtained on the testbed are presented to verify the effectiveness of the proposed method.

Capacitive-Based Contact Sensing for Office-Based Ventilation Tube Applicator for Otitis Media With Effusion Treatment

Otitis media with effusion is a prevalent condition affecting people of all age groups worldwide. When medication fails, a surgical procedure called myringotomy is done and a ventilation tube (grommet) is inserted. A novel all-in-one device that allows office-based myringotomy was conceptualized and realized, but there exists constraints with respect to contact sensing. This paper will discuss the challenges with contact sensing within the confines of the ear canal in the context of the applicator. A capacitive sensing approach is then proposed to circumvent these difficulties and experimental results are furnished to show the relative performance of capacitive sensing over force sensing for contact detection.

Integrated mechatronics design of flexure joint and controller in dual-drive gantry: A constrained H 2 optimization approach

The dual-drive H gantry is widely used in many industrial processes that require high precision Cartesian motion. The conventional rigid-link version suffers breaking down of joints if any de-synchronization between the two carriages occurs. To prevent above potential risk, a novel biaxial gantry with flexure-links is designed to allow a small rotation angle of the cross-arm. Nevertheless, the chattering of control signals and inappropriate design of the flexure joint will possibly induce resonant modes of the end effector. Thus, in this work, the design requirements in terms of tracking accuracy, biaxial synchronization, and resonant mode suppression are achieved by integrated optimization of the stiffness of flexures and PID controller parameters for a class of point-to-point trajectories with same dynamics but different steps. From here, an H2 optimization with defined constraints is formulated, and an efficient iterative solver is proposed by hybridizing direct computation of constrained projection gradient and line search of optimal steps. Comparative experiments results obtained on the testbed are presented to verify the effectiveness of proposed method.

A novel robust, continuous, PID-assisted control for precision tracking of flexible systems a case study on timing belts

Low-cost, indirect-drive actuators, like timing belts are widely used in many industrial applications requiring linear translational motion. However, the timing belt faces greater control challenges as newer technological processes necessitate an increased tracking accuracy, precision and a need for minimal vibration all in the presence of rapid payload changes. Firstly, it is widely known that belt dynamics contribute higher order modes to the system. This causes a non-collocated control problem where the encoder position on the motor side does not provide a good estimate of the end-effector position. Second, these higher order modes coupled with Coulomb friction associated with the end-effector makes system identification tedious and inviable. In addition, this makes control tricky as standard discontinuous robust techniques have a tendency to excite those higher frequency dynamics. Furthermore, they are used to carry payloads of varying mass and are loaded and unloaded in quick succession adding to model uncertainty. In order to achieve higher position tracking accuracy, the authors propose a continuous robust controller that compensates for higher order disturbance while having a DOB that handles lower frequency, friction-related dynamics of the timing belt. In this paper, the details of this control scheme, simulation results justifying our approach and relevant stability proofs are presented.