RESEARCH PAPER
Robotic hardness evaluation for natural materials
 
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Industrial Research Limited, P.O. Box 2225, Auckland, New Zealand
Publication date: 2021-08-27
 
Int. Agrophys. 1994, 8(4): 559–563
 
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ABSTRACT
The automated processing of natural products demands advanced sensing capabilities combined with well tuned responses. Many processes often require textural and positional information. In handling applications and in situations where guidance of a tool is required softness of the object plays an important role. This presentation reports on the development of a prototype sensor for hardness estimation. A relatively simple concept has been employed to probe the material. Measurements of a wide range of natural and flexible objects directed the design of the sensing head. The concept involves a dual tactile probe with selectable compliance to cover different ranges of hardness. Initial trials with a stationary sensor showed encouraging results. The sensor system has been mounted onto an industrial robot to examine continuous measurements during motion. The sensor data are fed back to the motion controller to guide the robot over a soft surface with a pre-selectable constant force. Experiments were conducted on flat and curved test beds with a variety of rubber-based materials. The results obtained showed good potential for force-controlled contour following applications. The major advantage of the sensing system is the capability to continuously identify the hardness range of an object as a function of the current position. Future developments are focusing on miniaturisation of the prototype sensor for 'real-world' applications and automatic orthogonal orientation of the sensor.
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