Projects (past)

• Traffic Characterization of Aperiodic Control Systems:

In networked systems, particularly over wireless or shared channels, the scarcity of communication resources makes the application of traditional control strategies with periodic sampling problematic. Alternative approaches with aperiodic sampling, such as: event triggered control and self triggered control, have been recently proposed to reduce network usage. Nonetheless, their features have not been exploited to propose less conservative hardware designs. Because hybrid nature of embedded systems along with aperiodic control executions lead to complicated infinite-state systems. In other words, deriving formal approaches for behavioral analysis of these systems is cumbersome. In this study, modeling the traffic generated by aperiodic control systems is of interest. By doing so, one can use the resulting models to guarantee correct functioning of networked control systems, for example in appropriate dimensioning of the underlying communication system or conducting schedulability analysis. We propose a technique to remove temporal and spatial dependencies to derive a timed automaton (or a quotient system) inspired by approaches in the literature. Based on the proposed construction technique, the timed automaton captures the timing behavior of the controlled system.

• Electro-Pneumatic Servo Control:

Electro-Pneumatic Servo Control Using On/Off Solenoid Valves:

Pneumatic actuators are higher-order nonlinear systems with mismatched uncertainties. Therefore, conventional nonlinear approaches as sliding mode control (SMC) are not applicable. Researchers have modified traditional nonlinear approaches during last decades to solve such problems. Higher-order and dynamical sliding mode are the examples of these modifications which address each dynamic and guarantee its stability. Another modified approach is a systematical developed method for nonlinear systems, called adaptive backstepping method. Here, a combination of sliding mode control and adaptive backstepping method to control a pneumatic actuator is used. One main contribution of this study was establishing a model-based servo pneumatic control system using on/off solenoid valves.

Air Pressure Control via Sliding Mode Approach Using an on/off Solenoid Valve :

Unique characteristics of servo pneumatic systems as compliance lead to growing application of them in numerous industrial fields. However, due to their higher-order nature and sever nonlinearities and uncertainties, researchers have been motivated to address servo pneumatic systems separately. In this aspect, an inner pressure control loop has been considered in many studies as a solution to encounter servo pneumatic systems. In this work, a nonlinear model-based approach is developed for controlling pressure of an actuator chamber. Through sliding mode control approach, the controller utilizes a 3/2 on/off solenoid valve to conduct the pressure control task. The performance of the proposed servo system is evaluated through several experiments and, also, compared with a proportional pressure regulator. Experimental results illustrate the competitive performance of the on/off solenoid valve with pressure regulator. The proposed servo system possesses more robust characteristics with respect to the proportional pressure regulator-included system. Furthermore, applying proposed approach, the cost, volume, and weight of controlling device are reduced, dramatically.

• Sensory Data Acquisition of Human During Walking and Biomechanics of Walking with rehabilitation application:

Intelligent Maker-based Motion Capture for Walking Pattern Recognition and Reconstruction:

We used an off-line marker-based motion capture technique for walking pattern recognition and reconstruction using only one camera. We used a neural network based approach for marker detection to reduce the need for human intervention in the process. This technique is applied to different performers walking on the treadmill in different slope conditions. Using pattern obtained from above process, we perform analyses between different performers in same positions and same performer in different positions. Finally, we transformed the obtained data to the BVH format for the reconstruction of performer’s motion that can be used in commercial animation tools.

The application of intelligent Based Motion Capture Technique: Kinematic Analyses and Gait Phase detection of Leg Joints in Three Different Gaits:

Motion capture techniques provide useful and practical information for analyzing different gaits and providing control inputs for rehabilitation instruments. Previously, we used an off-line marker-based motion capture technique for walking pattern recognition using SwissRanger-3000 camera. This technique was applied to different healthy performers walking on treadmill in various conditions. In this study, in order to conduct kinematic analyses, the raw neural networks data results are smoothed by means of periodic functions and, transitional and angular kinematic analyses are conducted on these smoothed outputs in the investigated different conditions. Using this technique, we propose a complete description for all joints during a gait cycle in the sagittal plane of motion. Furthermore, it has been observed that major differences between inclined slope gaits and straight gaits are during the midstance and terminal stance phases of gait cycles. One trend that can be used to extend our results is using discrete event approaches, such as PetriNets, to conduct gait phase detection based on introduced motion capture technique.

Constructing a Digital Encoder for Lower Limb Angular Movement:

Using IEL27 Incremental encoder and AtMEGA32 microcontroller, the angular displacement of knee and ankle joints are recorded. Two shafts are attached to the plates of encoder. Then, the encoder is placed on the joint position and each shaft is along with one of the related limbs. For example in the case of knee movement, shafts are along with the thigh and shin limbs and angular movement of the knee joint is calculated.