Pressure Sensor: State of the Art, Design, and Application for Robotic Hand

Hindawi Publishing Corporation Journal of Sensors Volume 2015, Article ID 846487, 12 pages http://dx.doi.org/10.1155/2015/846487 Review Article Pressure Sensor: State of the Art, Design, and Application for Robotic Hand Ahmed M. Almassri,1 W. Z. Wan Hasan,1 S. A. Ahmad,1 A. J. Ishak,1 A. M. Ghazali,1 D. N. Talib,1 and Chikamune Wada2 1 Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 2 Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan Correspondence should be addressed to Ahmed M. Almassri; and W. Z. Wan Hasan; Received 5 November 2014; Accepted 15 December 2014 Academic Editor: Guangming Song Copyright © 2015 Ahmed M. Almassri et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We survey the state of the art in a variety of force sensors for designing and application of robotic hand. Most of the force sensors are examined based on tactile sensing. For a decade, many papers have widely discussed various sensor technologies and transducer methods which are based on microelectromechanical system (MEMS) and silicon used for improving the accuracy and performance measurement of tactile sensing capabilities especially for robotic hand applications. We found that transducers and materials such as piezoresistive and polymer, respectively, are used in order to improve the sensing sensitivity for grasping mechanisms in future. This predicted growth in such applications will explode into high risk tasks which requires very precise purposes. It shows considerable potential and significant levels of research attention. 1. Introduction Robotic hand is a mechatronic machine that is made to complete assignment whenever it is required, especially for repetitive and dangerous tasks, and also during specific applications such as military robots, home automation [1], automotive industries, and nuclear industry robots. In fact, many robotic hand applications were already developed as in [2, 3]; for instance, dexterous manipulation [4–6], tactile image perception [7, 8], artificial limbs [9], fingerprint recognition [10], grasping objects [11–13], and pick and place applications [14, 15] can also be widely seen in various industries. Nonetheless, some of these robotic applications require a lot of labor force, notably in terms of assembly line and material handling. Henceforth, there is a significant need to have a dedicated machine, which is suitable for robust robotic application. For example, robotic hands manufacturing industries for pick and place mechanism are programed to complete task where it takes a product from one spot and put it to a different location. This technology has the advantages of reducing the risk process associated with human operators during the manufacturing process. Besides, it also saves time and energy required for the labor. Therefore, tactile sensing in the robotic hand is defined as a sensor device that is good enough to measure various properties of an object and provide information through physical touch between a sensor and an object [16]. Recently, the enhancement of the robotic hand sensor has received a substantial attention and becomes crucial to our everyday life. Researchers have recognized that equipping a robot with different sensors is a way to perform tasks in unstructured environment and enable the robot to cope with significant uncertainties. Due to the demand of ensuring safety between robots and objects during the mechanical touch, intelligent tactile sensing in robotic hand with high capabilities is critical. In this paper, the different techniques for measuring force or interface pressures are presented. These techniques include 2 Journal of Sensors load cells, pressure indicating film, and tactile pressure system. Similarly, a review on industry pressure sensing that involves the pick and place applications and algorithm control is also highlighted. The paper also discusses the MEMS sensor technology and different types of sensors while the last section of this part discusses the piezoresistive flexiForce sensor. FlexiForce sensor has a good substrate material, which is a polymer that enhances the force sensing and improves the performance of force, linearity, hysteresis, drift, and temperature sensitivity compared to any other thin film. Furthermore, it is flexible and ultrathin enough as the researchers and designers can use it in different integrated applications as well as for applications that are oriented to manipulative tasks with grippers of robotic hand. In a nutshell, new applications for tactile pressure sensing show a high increase in publications and research attention as viewed in Table 2. As a result, the design of sensor becomes more precise with higher reliability to overcome the problems. 2. Sense of Pressure: Methods Pressure is force per unit area applied in a direction perpendicular to the surface of an object. The formula is commonly written as follows: 𝑃= 𝐹 , 𝐴 (1) where 𝑃 is the pressure, 𝐹 is the normal force, and 𝐴 is the area of the surface of contact. When two objects are contacted, they exert force on each other. Thus, the average interface pressure is the total force divided by the interface region. In contrast, pressure measurement is necessary to get a peak pressure when the interface pressure is not uniformly distributed. In this context, there are three technologies and methods to be considered to measure force or interface pressures, load cells, pressure indicating film, and tactile pressure sensor. 2.1. Load Cell. Load cell is a type of pressure sensor, which is commonly used in industrial weighing product to measure force such as goods and vehicles. The gripper of a robotic hand that picks up an object can be equipped with load cells in order to provide compression force feedback to the control system which prevents damage to the object or released too early. Also, load cells can be used to measure the compression forces during a robot walk to provide data for the equilibrium-controlling system. In industrial machinery, rods, beams, wheels, and bars are instrumented in order to control the forces exerted on them. Due to this variety of possible applications, load cells are very important [23]. There are many types of technologies which are used to measure loads such as strain gauges, piezoelectric elements, and variable capacitance. Moreover, depending on the applied force and mechanics of application, multiple form factors of load cells are utilized. Typically, multiaxis MEMS force-torque sensors are used to measure the load. In the literature, a small number of multiaxis MEMS sensors have been reported. In [24], LC LC LC LC Fig (...truncated)