Robotic Systems - Applications, Control and Programming

Abstract

An autonomous anthropomorphic robotic arm has been designed and fabricated to automatically monitor plant tissue growth in a modified clonal micro-propagation system which is being developed for the New Zealand Institute for Plant & Food Research Limited. The custom-fabricated robotic arm uses a vertical linear ball shaft and high speed stepper motors to provide the movements of the various joints, with the arm able to swivel 180 degrees horizontally. Sensors located at the end of the arm monitor plant growth and the ambient growing environment. These include a compact colour zoom camera mounted on a pan and tilt mechanism to capture high resolution images, RGB (red, green and blue) colour sensors to monitor leaf colour as well as sensors to measure ambient atmospheric temperature, relative humidity and carbon dioxide. The robotic arm can reach anywhere over multiple trays (600mm x 600mm) of plantlets. Captured plant tissue images are processed using innovative algorithms to determine tissue, or whole plant, growth rates over specified time periods. Leaf colour sensors provide information on the health status of tissue by comparing the output with predetermined optimum values. Custom software has been developed to fully automate the operation of the robotic arm and capture data, allowing the arm to return to specified sites (i.e. individual plantlets) at set time intervals to identify subtle changes in growth rates and leaf colour. This will allow plant nutrient levels and the immediate environment to be routinely adjusted in response to this continuous sensing, resulting in optimised rapid growth of the plant with minimal human input. These low cost colour sensors can be incorporated into a continuous automated system for monitoring leaf colour of growing plants. Subtle colour changes can be an early indication of stress from less than optimum nutrient concentrations. In this chapter we also detail the calibration technique for a RGB sensor and compare it with a high end spectrophotometer.