Development and Evaluation of a Prototype Precision Harvesting Unit for Medicinal Plants – Tested on Hyssopus officinalis L.

Precision management of medicinal plant production using mechanical systems, processors, and sensors increases productivity, reduces waste, and properly manages production processes. This research developed a precision harvesting unit equipped with an automatic height adjustment system for utilization in harvesting machines to harvest Hyssop at an optimal height. The developed unit consists of a power transmission system (converting rotational motion into reciprocating motion), a harvesting platform (cutter-bar, reel, and conveyor) and a system to control the vertical movement of the head. An ultrasonic sensor was employed to detect the highest part of the plant for control purposes. A central control board and a driver were utilized to generate the control signal, while a stepper motor was installed as the actuator. Harvesting-related variables, including dry matter, essential oil content and yield, leaf-to-stem ratio as well as indices related to conservation agriculture were measured to evaluate the developed precision harvesting unit. Results showed that the unit increased the purity of the harvested plant raw material compared to manual harvesting of Hyssop which is important in extraction of the target substance such as essential oil. Steady-state error of the control system in adjusting the cutter-bar height for optimal height of harvesting Hyssop (T15) in elevation and descension modes was 2%.