Evaluation of Steering Characteristics of Smart Hand-Tractor with Inner Wheel Locking Mechanism

The two-wheeled hand-tractor, which is suitable for operation in small and irregular arable lands, is modified as a smart hand-tractor, or an agricultural robot. In unmanned operation under remote control or autonomous operation, un-like manned operation, movement of the smart hand-tractor is not adjusted by the operator gripping its handlebars with force. In this paper, a comparative experiment is conducted to confirm whether straight driving and tilling are possible in such unmanned operation as well as in manned operation. The authors' walking tractor is equipped with an inner wheel locking mechanism that not only disengages the power transmission to the inner wheel but also applies braking when turning, which is effective to ensure turning with a smaller radius on any ground with different rolling resistance. The experimental results showed that straight driving and tilling can be performed with the same quality regardless of the presence or absence of an operator and quantitatively showed that straight driving is adversely affected when tillage with a rotary hoe in the case of the authors' hand-tractor, in which the inner wheel locking mechanism is always activated during turning. It was found that the inner wheel locking mechanism should be dynamically enabled/disabled depending on the situation such as adjusting movement for straight and turning, in order to allow better autonomous operation of the hand-tractor.