MULTIDIRECTIONAL PNEUMATIC FORCE SENSOR FOR GRIPPERS Abstract CAEN, R.* and COLIN, S.** * Professor, Institut National des Sciences Appliquees de Toulouse- Departement de Genie Mecanique. Avenue de Rangueuil, 31077 Toulouse Cedex, FRANCE. ** Researcher, Institut de Mecanique des Fluides. Allee du Professeur Camille Soula, 31400 Toulouse, FRANCE. The aim of this paper is to present an original multidirectional pneumatic force sensor based on the pneumatic potentiometer effect. It allows a gripper to maintain an object with the minimum necessary gripping force. The sensor is able to detect the forces due to the carried object (weight, inertia forces) which are directed in any direction in a plane perpendicular to the sensor axis. This detection in a whole plane considerably increases the possibilities of the I.M.F.T. Pneumatic Prehensor. Key Words Force, acceleration, pressure, sensing systems, prehensors, grippers, robotics. Introduction A pneumatic prehensor has been studied in the Fluidics and Jets Dynamics team of the lnstitut de Mecanique des Fluides de Toulouse, for a few years. It is able to self-evaluate the grasping force required for the various phases of the objects manipulation. This prehensor has obtained an international patent [1] and some distinctions [2]. Two sensors can be used as shown in Fig. 1 : a contact sensor described in paper [3] and an unidirectional force sensor described in paper [4], the behavior of which is the following. A determined unbalance between the two pneumatic potentiometers allows an initial gripping force when the mobile finger comes in touch with the object. Its value is about one Newton. As soon as the robot wrist moves up, the blade bends down, the pressure increases in the lower potentiometer and decreases in the upper one. Thus the acting force of the jack on the object increases gradually until the object takes off. This phase can be short (about 0.1 s). This prehensor is performing but the unidirectional sensing limits its degrees of freedom number. For that purpose, a multidirectional force sensor which can take the place of the unidirectional one has been realized. It allows the prehensor to keep its tactile sense in a whole plane and so it increases considerably the gripping possibilities of the manipulators, by adding three degrees of freedom to the wrist. S. G. Tzajestas (ed.). Robotic Systems. 551-558. © 1992 Kluwer Academic Publishers. 551