Roberto Oboe

Sensorless full-digital PMSM drive with EKF estimation of speed and rotor position

This paper concerns the realization of a sensorless permanent magnet (PM) synchronous motor drive. Position and angular speed of the rotor are obtained through an extended Kalman filter. The estimation algorithm does not require either the knowledge of the mechanical parameters or the initial rotor position, overcoming two of the main drawbacks of other estimation techniques. The drive also incorporates a digital d-q current control, which can be easily tuned with locked rotor. The experimental setup includes a PM synchronous motor, a pulsewidth modulation voltage-source inverter, and floating-point digital-signal-processor-based control system.

A Design and Control Environment for Internet-Based Telerobotics

This paper describes an environment for the design, simulation, and control of Internet-based force-reflecting telerobotic systems. We define these systems as using a segment of the computer network to connect the master to the slave. Computer networks introduce a time delay that is best described by a time-varying random process. Thus, known techniques for controlling time-delay telerobots are not directly applicable, and an environment for iterative designing and testing is necessary. The underlying software architecture sup ports tools for modeling the delay of the computer network, design ing a stable controller, simulating the performance of a telerobotic system, and testing the control algorithms using a force-reflecting input device. Furthermore, this setup provides data about including the Internet into more general telerobotic control architectures. To demonstrate the features of this environment, the complete proce dure for the design of a telerobotic controller is discussed. First, the delay parameters of an Internet segment are identified by prob ing the network. Then, these parameters are used in the design of a controller that includes a quasi-optimal estimator to compensate small data losses. Finally, simulations of the complete telerobotic system and emulations using a planar force-reflecting master and a virtual slave exemplify a typical design-and-test sequence.

Stability Analysis and Practical Design Procedure of Time Delayed Control Systems With Communication Disturbance Observer

In a research field of network-based control systems (NBCSs), the time delay problem is one of the most significant issues. Efficient stabilization methods of time delayed control systems enable NBCSs to be flexibly applied to many kinds of situations. A novel time delay compensation method based on the concept of network disturbance (ND) and communication disturbance observer (CDOB) has been proposed. The compensation method has the same effectiveness as that of the Smith predictor. In addition, since the method is simple and does not need time delay model or time delay measurement, it can be easily implemented to various applications. However, the design method has not been concerned so far. This paper therefore presents stability analysis and studies a practical design procedure of the time delayed control systems with CDOB. At first, the concept of ND is introduced and the validity of the time delay compensation method is described. Then an analysis about the effects of parameters in control systems on stability is conducted. Characteristics of the effects of parameters on stability come out. Then we study a practical design procedure of the time delayed control systems. The validity of the design procedure is validated by experimental results. In the experiment, we also verify the performance of the system in the case of time-varying delay. Finally, comparative study of the method to the Smith predictor is presented.

Architectures for shared haptic virtual environments

Abstract The lack of force feedback in visual-only simulations may seriously hamper user proprioception, effectiveness and sense of immersion while manipulating virtual environments. Haptic rendering, the process of feeding back force to the user in response to interaction with the environment is sensitive to delay and can become unstable. In this paper we will describe various techniques to integrate force feedback in shared virtual simulations, dealing with significant and unpredictable delays. Three different implementations are investigated: static, collaborative and cooperative haptic virtual environments.

Web-interfaced, force-reflecting teleoperation systems

An ever-growing number of Internet-connected devices is now accessible to a multitude of users. Being a ubiquitous communication means, the Internet could allow any user to reach and command any device connected to the network. This paper reports the successful application of real-time closed-loop control over the Internet in the Java Based Interface for Telerobotics (JBIT) system, in which Internet users can access and command a two-degrees-of-freedom robot in real time, receiving both visual and force feedback. When the closed-loop control of a remote system comes into play, careful evaluation of the performance and limits of the communication system in use is mandatory. The analysis reported shows that the main limits of the Internet are the unknown available throughput, the variable delay, and the loss of some data packets, in particular, when the network is congested. Once the limits of the communication system are known, it is shown that it is possible to use the Internet for the remote closed-loop control of a slave robot, provided that suitable strategies to guarantee operability and safety of the controlled system have been implemented. The strategies implemented in order to overcome the limits posed by the present Internet characteristics are described, along with an improved coordinating force control scheme, which enhances the transparency of the teleoperator.

Towards Tactile Sensing System on Chip for Robotic Applications

This paper presents the research on tactile sensing system on chip. The tactile sensing chips comprise of 5 × 5 array of Piezoelectric Oxide Semiconductor Field Effect Transistor (POSFET) devices and temperature sensors. The POSFET devices are obtained by spin coating piezoelectric polymer, poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), films directly on to the gate area of Metal Oxide Semiconductor (MOS) transistors. The tactile sensing chips are able to measure dynamic contact forces and temperatures. The readout and the data acquisition system to acquire the tactile signals are also presented. The chips have been extensively tested over wide range of dynamic contact forces and temperatures and the experimental results are presented. The paper also reports the research on tactile sensing chips with POSFET array and the integrated electronics.

Experimental Analysis of an Internet-Based Bilateral Teleoperation System With Motion and Force Scaling Using a Model Predictive Controller

This paper presents an experimental investigation of a bilateral generalized predictive controller for scaled teleoperation systems subject to slave force feedback, variable transmission-time delays, and packet losses. The originality of the approach proposed mainly lies in its capacity to take into account explicitly the slave force feedback in the predictive algorithm. Experimental results show the system stability with the proposed approach using a frequency-domain technique. Several configurations of scaling factors have been used; it is shown that the stability conditions strongly depend of the external environment. Another experimental result verify the robust performances of the approach in terms of tracking behavior with both strong variations of time delays and packet losses in the communication network. For the experimentations, the communication network is the Internet using user-datagram protocol, while the slave robot is a 6-DOF anthropomorphic robot with a force sensor.

Control of a Z-axis MEMS vibrational gyroscope

The paper describes the design of the control loops in a Z-axis, MEMS vibrational gyroscope. In this device, a silicon mass is driven through electrostatic actuator so that it has a sinusoidal linear motion, with a controlled speed. The design of a suitable controller, capable of maintaining the required speed and with prescribed restoring capabilities after shocks has been derived and described in the paper. Attached to the driving mass, a second mass, free to move in the direction orthogonal to the motion of the first mass, is subjected to a Coriolis force, proportional to the product of the first mass speed by Z-axis rotational speed. The sensing of the Coriolis force and, in turn, of the Z-axis rotational speed, is performed in closed loop fashion, with a 1-bit quantized actuation. The restoring force that brings the motion of the second mass to zero is equivalent to the output bit stream of a sigma-delta converter and contains the information of the Coriolis force. The design of this second control loop and a detailed analysis on the signal-to-noise ratio achievable with the proposed design is reported.

Internet-based telerobotics: problems and approaches

This paper describes the main issues facing the development of telerobotics systems connected to the Internet. The initial hurdle relates to the definition and implementation of an appropriate communication protocol for delivering real-time data. Two of the solutions proposed in the literature are briefly summarized. Then the paper examines the issues relevant to control systems in the presence of time delay, with particular reference to telerobotic systems with force feedback. The delay introduced by Internet connections have specific characteristics that are briefly summarized, together with the control theory approaches available to design stable algorithms. Finally, we present the results of experiments aimed at representing typical Internet connections in terms of parameters useful for the design of a control systems.

Automatic Mode Matching in MEMS Vibrating Gyroscopes Using Extremum-Seeking Control

In order to enhance the sensitivity and to reduce the readout circuit complexity of any angular velocity microsensor (vibrating gyroscope), it is crucial to reduce the frequency mismatch of its resonant modes of vibration. Achieving a good matching accuracy during fabrication is rather difficult because of tolerances and process variations that detrimentally affect the manufacturing precision. Moreover, even assuming to achieve a good frequency matching through fabrication or postfabrication calibration, it is very likely that parametric variations induced by the external environment during the normal operation of the device disrupt any initial tuning. For these reasons, in this paper, an alternative way to accomplish the frequency-matching condition is suggested, which exploits a real-time adjusting mechanism based on an automatic mode-matching control loop. In particular, this paper describes the details of an adaptive controller capable of automatically matching the resonant frequencies of the two main modes of vibration of a single-axis vibrating microgyroscope, under the provision that there is an underlying mechanism through which the frequency mismatch can be controlled by adjusting a suitable tunable parameter. The controller is designed by considering the requirement of reducing its complexity, so that it can be easily implemented on cheap sensors. Owing to a key observation that allows the recast of the frequency-matching problem as a maximization problem, the proposed mode-matching controller is actually designed as a standard perturbation-based extremum-seeking controller, which can be implemented by using few analog electronic components. The proposed solution has been tested on the LISY300AL yaw-rate microelectromechanical system gyroscope manufactured by STMicroelectronics, showing that a mode matching of nearly 1 Hz or less can be easily attained.