This paper describes an embedded system for the automation of scheduling systems such as school bells, factory shift changes, military drills etc. The system consists of two parts: a remote node used for remote control and setup of the system and the real time actuator node which controls a physical object, for example, a bell system. The hardware and software structure are illustrated in detail for both parts of the system through the implementation as an automatic school bell system.

This paper is concerned with the force control of a walking piezoelectric motor, a commercially available Piezo LEGS motor. The motor is capable of providing high precision positioning control on nanometer scale, but also relatively high forces up to 6 N. The proposed force control algorithm is very simple, but effective, and it is based on a recently presented coordinate transformation. The transformation allows definition of the driving waveforms for the motor according to a desired motion of the motor legs in the plane of motion. Such a possibility opens a path for creating the y-direction interaction force between the motor legs and the rod which is enough to ensure no relative motion between the legs and the rod. Once that is achieved, one can control the x-direction force imposed by the motor rod on its environment. The presented force control scheme has been successfully validated through a series of experiments.

This paper presents a compact and low cost digital signal controller (DSC) based implementation for power control of a doubly fed induction generator (DFIG) based wind energy setup for micro-grid applications. The experimental setup consists of a back to back converter, a 1.1 kW DFIG and two low cost, industry standard DSCs. Stator active power and reactive power are controlled by means of the rotor currents. Decoupled components of the rotor current in a rotating frame are controlled by a robust, disturbance observer based control structure. The proposed controller was validated through experiments.

A novel approach for formation control of differential-drive mobile robots is presented in this paper. The control design is done in the framework of functionally related systems. Functionally related systems are the systems that are `virtually' interconnected. The term `virtually' denotes the situation in which the states or outputs of otherwise separated systems are functionally related to each other. If a formation of mobile robots is analyzed, it can be considered as a group of functionally related systems. Therefore, formation control of the robots can be synthesized in the mentioned framework.

This paper offers a new approach for specifying the waveforms of driving voltages for a Piezo LEGS motor. A novel idea of coordinate transformation to define the waveforms of driving voltages, based on the motor static model, is presented. This transformation defines driving voltages according to the desired motion of the motor legs in the x- and y-directions. The approach allows a user to first define force acting on the motor rod in the y-direction and define the rod's x-direction trajectory profile. Waveforms of the driving voltages are subsequently defined to meet these requirements. The proposed approach also enables the possibility of defining the desired step shape for the motor and, according to that definition, producing driving voltages. Based on the given coordinate transformation, a simple method for Piezo LEGS motor control, identified as virtual time control, is presented. This method results in overshoot-free high precision positioning.

In this paper implementation of a control system for high precision applications is presented. The control system is developed for a Piezo LEGS motor, which is a walking piezo motor that can be employed in nanometric precision applications. In the control system structure, two main components are digital signal controller which executes control algorithm and power driver that is generating driving voltages for the motor. The waveforms of the driving voltages are designed using a recently presented coordinate transformation. This transformation enables synthesis of driving waveforms according to design requirements regarding force imposed to the motor's rod and rod's x-direction trajectory profile. In this work, the waveforms are selected to ensure no relative motion between the motor's legs and rod, and constant velocity of the rod within one step. Control algorithm is named as virtual time control. Despite its simplicity, the algorithm allows high precision positioning which is very close to theoretically achievable one.

When a complex task has to be performed by multiple systems, it imposes functional dependencies between the states and outputs of the systems. These functional dependencies create a system of 'virtually' interconnected subsystems, even though they may be physically separated. The component subsystems within the overall system we call 'functionally related systems', since nature of the task of the system is defining functional relations between the system components. This dissertation deals with motion control design for functionally related systems. The design is based on identifying functions to be executed within a task and design of control to make these functions follow their references. The main goal is to obtain unit control distribution matrix in the function space and enforce a desired dynamics for each of the identified functions. However, the decoupling is not based on physical separation, but rather on the functions. By transforming the configuration space dynamics of the controlled system to the function space, it is shown that by properly selected transformation one can obtain the desired structure of the dynamics in the function space which has identity control distribution matrix. This was done by projecting the configuration space velocities to the function space by the function Jacobian matrix, and having transformation of the control signals from the function space back to the configuration space by a right pseudoinverse of the function Jacobian matrix. In the presented approach, any right pseudoinverse of the function Jacobian matrix can be used. A weighted pseudoinverse is proposed in this dissertation; thus, a weighting matrix can arbitrarily be selected. While any appropriate control method can be used for control input synthesis in the function space, three control methods were employed in this dissertation. These are disturbance-observer-based control, sliding mode control, and control based on the equivalent control estimation. All these methods provide stable and robust control in the function space. The proposed approach for control design is tested in experiments and simulations. Experimental results on a piezoelectric walker showed that nanometric precision positioning can be achieved. In experiments for tasks including two pantograph manipulators, results validated the presented approach allowing simultaneous grasping force and motion control. Simulation results for different tasks including different robotic manipulators and for the formation control of mobile robots showed the potential of our proposed methods in some other interesting scenarios as well.

In this paper a novel design for three-dimensional (3-D) contour controller is proposed. This design relies on dynamics projection to the moving Frenet-Serret frame defined for each point on reference trajectory. Contour controller consists of independent joint controller and additional sliding mode controller, added as corrective term. Control task is defined as contour tracking with constant tangential velocity. Contour controller was compared with independent joint controller designed as acceleration controller with first order disturbance observer. Reference trajectory is generated using time based spline approximation to provide smooth reference trajectory. Experimental results showed significant improvement that contour controller provides over independent joint control with relatively high velocity references.

This work presents a modular and reconfigurable desktop microfactory for high precision machining and assembly of micro mechanical parts. Miniature factory is inspired by the downsizing trend of the production tools. The system is constructed based on primary functional and performance requirements such as miniature size, operation with sub-millimeter precision, modular and reconfigurable structure, parallel processing capability, ease of transportation and integration. Proposed miniature factory consists of several functional modules such as two parallel kinematic robots for manipulation and assembly, galvanometric laser beam scanning system for micromachining, camera system for inspection, and a rotational conveyor system for sample part delivery. The overall mechanical structure of the proposed microfactory facilitates modularity and reconfigurability, parallel processing, flexible rearrangement of the layout, and ease of assembly and disassembly of the whole structure. Experiments involve various tasks within a single process such as pick-place of the 3 mm diameter metallic ball, marking a 2D sub-millimeter image on the ball surface with high power laser, and inspection along with verification of the image by means of microscopic camera. Results have shown the possibility of implementation of the desktop microfactory concept for machining and assembly of tiny mechanical parts with microprecision.

This paper describes FPGA based control system for a piezoelectric motor, commercially available Piezo LEGS motor. Driving voltages waveforms are defined as a combination of linear functions. This definition provides possibility for easy implementation on very simple hardware. Linear functions parameters allow forming of the driving voltages according to desired trajectory of motor's legs. Considering that FPGA technology offers many advantages over the classical microprocessor based systems, it is used as control system implementation hardware. Realized control system can be very easily expanded to control multiple motors, if hardware resources are big enough. Also modularity is provided, making the future application very simple. In the paper control system structure is described in detail along with a very simple control algorithm for Piezo LEGS motor positioning control. Experimental results are given to validate designed control system. They showed satisfying control performance, responses with no overshoot and expected steady state error.

This work focuses on the design of driver for PiezoLegs actuator used for high precision positioning purposes. Motor is driven with the set of periodical voltages with known frequency, amplitude and phase shift between the phases. Motor's operation has been investigated in detail and clear relationships between the amplitude and phase shifts between the driving voltages and motor step size have been established. According to the motor analysis, set of design requirements for the design of driver is given. Particular solution meeting these requirements and satisfying the given design constraints is presented. Driver is experimentally evaluated for power consumption and analyzed in frequency domain, it's performance is compared to the performance of a commercially available driver for the same motor. Designed driver shows improved performance.

This paper describes configuration space control of a Delta robot with a neural network based kinematics. Mathematical model of the kinematics for parallel Delta robot used for manipulation purposes in microfactory was validated, and experiments showed that this model is not describing “real” kinematics properly. Therefore a new solution for kinematics mapping had to be investigated. Solution was found in neural network utilization, and it was used to model robot's inverse kinematics. It showed significantly better mapping between task space coordinates and configuration (joint) space coordinates than the mathematical model, for the workspace of interest. Consequently positioning accuracy improvement is expected. Neural network is then used as a part of the control system. Applied control strategy was configuration space acceleration control with disturbance observer.

This work presents functional description of a walking piezoelectric motor and its control in nanometer precision. For this purpose a dynamical model of the actuator is derived based on simple mass spring damper system. Model parameters are estimated from step response plot and the system is expressed with second order transfer function. Additional identification experiments verified the theoretical kinematics of the bimorph legs. These experiments demonstrate approximately linear relation between the legs displacement in x and y directions to the applied voltages. Based on derived system model and identification results a PI controller followed by Hadamard transformation is proposed as a controller scheme. Experimental results for staircase and sinusoidal references reveal precise positioning capabilities of the system with the proposed control scheme down to few nanometers.

This work presents functional description of a walking piezoelectric motor and its control in bending mode. For this purpose a dynamical model of the actuator is derived based on simple mass spring damper system. Identification experiments are conducted to verify the theoretical kinematics of the bimorph legs presented in previous works. These experiments demonstrate approximately linear relation between the legs displacement in x and y planes to the applied voltages. Based on these results a PI controller followed by Hadamard transformation is proposed as a controller scheme. Experimental results for staircase and sinusoidal tracking references reveal precise positioning down to few nano-meters.