Smart Actuators in Robotics

Piezoelectric solid-state actuators continue to gain in technical and economic significance for a great variety of applications such as quick fine-positioning tasks, control of structural stability and active noise and vibration control due to the high driving forces, short reaction times and compact construction of these actuators. Microelectronics and signal processing must be combined intelligently to form `smart actuators' in order to do justice to the growing demand for precision, miniaturization, efficiency and cost. Energy transducers with piezoelectric PZT ceramics (PZT: lead-zirconate-titanate) simultaneously possess actuator and sensor capacities. An important requirement for the construction of smart actuators is fulfilled by separating the sensor information (charge approximately external force) from the actuator control quantities (elongation approximately electric field strength). A closed-loop control structure with digital signal processing and a voltage controlled power amplifier were developed to enable nearly load-independent linearization of the actuator's response characteristic (elongation-voltage curve) even under dynamic operating conditions by making use of the `self-sensing' effect and without using extra force or displacement sensors. The effectiveness of the developed approach for realizing smart actuators was verified and specified with the help of a computerized large-signal measurement set-up using a low-voltage piezoelectric ceramic stack as an example.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Significant advances in smart material actuators have taken place in the past decade. The holy grail of actuator research is an architecture that can generate high displacement and force throughout a broad frequency range while not consuming a significant amount of electrical power. The large appeal of using smart material actuators stems from their high mechanical energy density. However, all smart material actuators generally have at least one shortcoming involving either mechanical stroke, force, or frequency capability. Whenever speed is a consideration, piezoelectric actuation is the most commonly employed. The purpose of this paper is to review the most current trends in piezoelectric actuation architectures. The paper does not present the theoretical details of each actuator, but instead strives to highlight the novel concepts used in each design to overcome the stroke limitation of the material.

Hysteresis phenomenon occurs in all smart material-based sensors and actuators, such as shape memory alloys, piezoceramics and magnetostrictive actuators (Bank & Smith, 2000; Tan & Baras, 2004). In order to study this phenomenon, different models were proposed (Brokate & Sprekels, 1996; Visintin, 1994). Normally, hysteresis models are classified into two categories, physics-based model such as Jiles-Atherton model (Jiles & Atherton, 1986) and phenomenology-based model such as Preisach operator (Brokate & Sprekels, 1996; Visintin, 1994) and Duhem model (Visintin, 1994). From control systems point of view, hysteresis is generally non-differentiable, nonlinear, and unknown. As a result, systems with hysteresis usually exhibit undesirable inaccuracies or oscillation and even instability. Mitigating the effect of hysteresis becomes necessary and important, thus it has received increasing attention in recent years (Tao & Kokotovic, 1995, Su, et al, 2000, Su, et al, 2005). Many of these studies are related to modeling of hysteresis and their control issues. With the development of artificial intelligent (AI), AI is being applied to dealing with nonlinearities in systems (Ge & Wang, 2002). Only a few studies have been carried out by using NN to tackle hysteresis modeling and compensation (Makaveev, et al, 2002; Kuczmann & Ivanyi, 2002; Beuschel et al, 1998; Zhao & Tan, 2006). In the paper (Makaveev, et al, 2002), a NN model is used to describe the hysteresis behavior in different frequencies with the knowledge of some properties of magnetic materials, such as loss separation property to allow the separate treatment of quasi-static and dynamic hysteretic effects. Beuschel et al used (Beuschel et al, 1998) a modified Luenberger observer and NN are used to identify a general model of hysteresis. These researches demonstrate that NN can work as an unknown function approximator to describe the characteristics of hysteresis. Recently, two papers (Zhao & Tan, 2006; Lin et al 2006) applied the approximation property of NN to coping with the identification of Preisach-type hysteresis in piezoelectric actuator, and the hysteresis estimation problem for piezo-positioning mechanism based on hysteresis friction force function, respectively. It should be noted that the aforementioned results share a common assumption that the output of hysteresis is measurable. In practical systems, smart actuators are integrated into the systems, which makes the measurement of output of hysteresis hard. Hence it is a challenge to design an observer for

The concept of microwave-driven smart material actuators was envisioned anddeveloped as the best option to alleviate the complexity and weight associatedwith a hard-wire-networked power and control system for smart actuator arrays.The patch rectenna array was initially designed for high current output, but hasundergone further development for high voltage output devices used in shape controlapplications. Test results show that more than 200 V of output were obtained from a6 × 6 array at a far-field exposure (1.8 m away) with an X-band input power of 18 W. The6 × 6 array patch rectenna was designed to theoretically generate voltages up to 540 V,but practically it has generated voltages in the range between 200 and 300 V.Testing was also performed with a thin layer composite unimorph ferroelectricdriver and sensor and electro-active paper as smart actuators attached to the6 × 6 array. Flexible dipole rectenna arrays built on thin-film-based flexible membranes are mostapplicable for NASA’s various missions, such as microwave-driven shape controls foraircraft morphing and large, ultra-lightweight space structures. An array of dipolerectennas was designed for high voltage output by densely populating Schottky barrierdiodes to drive piezoelectric or electrostrictive actuators. The dipole rectenna array willeventually be integrated with a power allocation and distribution logic circuit andmicrobatteries for storage of excessive power. The roadmap for the development of wirelesspower drivers based on the rectenna array for shape control requires the development ofnew membrane materials with proper dielectric constants that are suitable for dipolerectenna arrays.

This paper proposes position and force sensors of the haptic interface for training simulation of radial artery puncture. The position sensor with two optocouplers and one code stick is designed to measure translational movement of the guidewire. The position sensor can measure linear motion with speed up to 160mm/s with 1mm error. The resolution of the designed position sensor is 0.195mm. A leverage structure of the designed force sensor is employed with two force sensitive resistors (FSR) to measure the interaction force. The force sensor can measure 0∼10N in the needle-insertion direction, and 0∼5N in the needle-withdrawal direction. The force sensing errors are 8.85% and 12.22% in the needle-insertion and needle-withdrawal directions, respectively. The RMS errors are 0.52N and 0.37N for each direction.

Smart actuators, made of smart materials, are becoming more attractive in many applications because smart materials are not subjected to wear and does not require lubrication during services. Piezoelectric materials are a group of the many attractive smart materials that are being investigated for many applications today. Piezoelectric materials show fast responses, high efficiency/accuracy and operate on a large bandwidth. Composite materials are of interest because of their design flexibility and because they are lighter than other materials commonly used in aircraft and other applications. For the research reported here, a piezoelectric material was embedded in a composite material to form a piezoelectric composite actuator. This research was conducted to expand our knowledge of piezoelectric composite material actuators, and originated from the need to control air flow separation over an airfoil. There is a need to build a profound knowledge about such actuators before they can be implemented in an airfoil, and to understand which parameters influence the behaviour of piezoelectric composite material actuators under static and dynamic operating conditions. The actuators were manufactured and tested under static and dynamic conditions and the experimental results were compared to the finite element models. The models were incorporated with piezoelectric material properties that were determined experimentally. The results showed that a piezoelectric material’s response to an input stimulant, e.g. electric voltage and frequency, influences the actuator’s behaviour.

In order to realize a high accuracy space structure system, shape and vibration controls using smart structures are studied. Two prototypes of smart reflectors were developed and investigated. One was a long smart beam system equipped with Macro Fiber Composites (MFCs) and the other was a smart reconfigurable reflector equipped with smart actuators. The smart actuator was designed for the smart reconfigurable reflector and it consisted of a piezoelectric stack actuator and a displacement magnification mechanism. Experiments of the shape and vibration controls of the long smart beam were carried out and their performance were investigated. The performance of the smart actuator was also investigated through numerical simulations and experiments. The results are reported in this paper.

Active surface adjustment of cable net structures is becoming significant when large-size cable net structures are widely applied in various fields, especially in satellite antennas. A general-duty adjustment method based on active cables is proposed to achieve active surface adjustment or surface profile reconfiguration of cable net structures. Piezoelectric actuators and voice coil actuators are selected for constructing active cable structures and their simplified mechanical models are proposed. A bilevel optimization model of active surface adjustment is proposed based on the nonlinear static model established by the direct stiffness method. A pattern search algorithm combined with the trust region method is developed to solve this optimization problem. Numerical examples of a parabolic cable net reflector are analyzed and different distribution types of active cables are compared.

Comparison of energy consumption and specific energy requirements of different methods for drying mushroom slices

The batch annealing process is used for heat treatment of coils output of the cold rolled process. In this process, high speed fan motors are used to generate strong convection currents and thermal heat convergence in all coil layers. Several factors could affect product quality grade. In this work by changing the motor speed, optimal frequency is reported to have the highest quality convergence and lowest energy consumption. For testing, frequencies of 45, 55, 65 and 75 Hz were tested. The results showed that there is highest quality convergence and lowest electrical energy consumption in frequency of 55 Hz. The practical solution represented in this work can be used to achieve optimal frequency for each condition.

The traditional way of controlling an industrial robot is to program it to follow desired trajectories. This approach is sufficient as long as the accuracy of the robot and the calibration of the workcell is good enough. In robotic assembly these conditions are usually not fulfilled, because of uncertainties, e.g., variability in involved parts and objects not gripped accurately. Using force control is one way to handle these difficulties. This paper presents a method of doing force control without a force sensor. The method is based on detuning of the low-level joint control loops, and the force is estimated from the control error. It is experimentally verified in a small part assembly task with a kinematically redundant robotic manipulator.

Design and manufacturing of mobile micro manipulation system with a compliant piezoelectric actuator based micro gripper

An Optoelectronic System for Force-Torque Sensing and Feedback Algorithms Processing

The goal of this research is to develop a new haptic interface device, which can improve operability and expressiveness of personal computer (PC). A new mouse type device named active mouse is developed. It consists of one omni-traveling mechanism, force sensor, position sensor and communication and control system. The omni-traveling mechanism consists of one sphere ball, two differential mechanisms, and two motors. This mechanism realizes rotation of one motor that will not affect the other motor. Therefore, output of the two motors can be composed as output to the ball. As a result, this omni-traveling mechanism can achieve 4.8[N] force at 5[V] and 500 [mAJ in compact size. The two motors of omni-traveling mechanism, force sensor and position sensor are controlled with communication and control modules developed in this research. The communication system for Active Mouse equips with USB interface. The USB interface supplies DC voltage and support communication with PC. Therefore this device can be used for general PC just connecting USB interface. To confirm function ability of the Active Mouse, a graphical program is developed. Using this program, Active Mouse can input user's force and position data to PC, and output force to user. From here, Active Mouse realizes functions of general mouse and also works as haptic device.

With climate change concerns on the rise, finding efficient and sustainable ways to separate carbon dioxide from industrial gas mixtures has become increasingly important. Membrane‐based gas separation technologies offer a promising solution due to their low energy consumption, low emissions, and ease of operation. In this study, we dug deep into theoretical energy consumption and practical optimization strategies for CO2 separation using such technologies. Our results showed that CO2 separation can be achieved with relatively low specific energy consumption, ranging from 0.09 to 0.27 MJe/kg CO2, depending on feed CO2 concentration. By conducting process simulations, we determined the optimal feed gas pressure and membrane surface area required to achieve a CO2 absorption ratio of 90% (mol). We also analyzed the effects of CO2 permeation and selectivity on energy consumption and membrane area, revealing that increasing both can significantly reduce energy consumption, albeit with more membrane surface area required. Using seepage flow circulation was found to be a particularly effective way to improve feed CO2 concentration and reduce energy consumption. To optimize and improve the capturing process, we conducted exergy analysis in each of the five stages of optimization, reporting Cooling Utilities (MW), Heating Utilities (MW), and Total Utilities (MW) for each step. Our results showed that in the optimal mode, Total Utilities (MW) were reported as 228.1, highlighting the potential of membrane‐based CO2 separation for carbon capture and storage applications. This study provides valuable insights and practical strategies for achieving efficient and sustainable CO2 separation.