Stiffness Analysis of Underactuated Fingers and Its Application to Proprioceptive Tactile Sensing

Abstract

Underactuation has become, in recent years, more and more prevalent in robotic fingers since it provides the latter with the ability to mechanically adapt to the shape of the objects seized. To improve the usually simplistic control schemes of these fingers, and possibly to provide force feedback or control, tactile sensors are typically used. However, another promising avenue, as presented in this paper, is rather to use information provided by proprioceptive (i.e., internal) sensors. Most interestingly, this can be done using only the torque and position sensors typically found attached to the actuator(s) of these fingers. Because a relationship exists between the stiffness of an underactuated finger as seen from its actuator and the contact locations on its phalanges, it is possible to estimate one from the other. In this paper, a proprioceptive tactile sensing algorithm based on this technique is presented. It is concluded that within certain theoretical and practical limits, it is possible to extract tactile data from a self-adaptive finger, namely position and magnitude of the contact forces, without actually using any physical tactile sensors.

Visual Pressure Estimation and Control for Soft Robotic Grippers

“…Prior work has used internal sensors to infer contact and pressure based on deformation of the gripper's surface [10], [11], [12], [13], [14], [15], [16], changes to gripper vibrations [17], deflection of the gripper's compliant joints [18], [19], [20], [21], and changes to the gripper's motion [22], [23]. We expect that our method can use similar information by observing a soft gripper with an external camera.…”

Hierarchically patterned self-powered sensors for multifunctional tactile sensing

“…Inferring material properties of objects is needed for many industrial and medical conditions (19,20). A number of technologies, including various image pattern recognition methods and machine learning technology, have been implemented in material identification (21)(22).…”

Fast Terminal Sliding Control of Underactuated Robotic Systems Based on Disturbance Observer with Experimental Validation

“…Underactuated systems are categories of nonlinear dynamic systems which have fewer number of actuators than degrees of freedom [1][2][3][4][5]. The stabilizer and tracker design problems of these dynamical structures involve wide investigation due to their application in flexible manipulators [6], marine vessels [7], robotics [8,9], aircraft assembly [10], hovercraft [11], legged locomotion [12], overhead crane [13], satellite [14], rigid spacecraft [15], inverted pendulum [16], aeroelastic wing section [17], underwater vehicles [18], surface vessels [19], quad-rotors [20,21], flexible joint robots [22], cranes [23], visual servoing [24], proprioceptive tactile sensing [25], vertical take-off and landing drones [26] etc. Due to low numbers of actuators, the used energy and complexity of underactuated systems are less than fully actuated systems.…”