Design and implementation of a Kalman state estimator for balancing of uniaxial vehicles for goods transport

Uniaxial vehicles for goods transport such as hand trucks offer intuitive manoeuvrability with little space requirements and the ability to overcome obstacles such as steps and kerbs. This is why this class of vehicles is popular with many transport tasks. The disadvantage of this pedestrian controlled means of transportation is the need for the user to apply the force for stabilisation and propulsion. A solution approach is to equip the uniaxial vehicle with a controlled drive system providing force for both stabilisation and propulsion. To realise such balance control the vehicle frame's pitch angle must be adopted with every change of load. This is a fundamental difference to uniaxial vehicles without payload or for passenger transportation. In this paper we present a Kalman state estimator for identification of the frame's and load's combined center of gravity's pitch angle. It is not measureable using sensors installed on the vehicle frame but must be known for the vehicle's balance control. The estimator was designed and implemented using our new uniaxial vehicle system for freight transport. The experimental results show the correct operation of the approach. The estimator provides a basis for further research in the field of control strategies both for stable operation of this type of vehicle under real-life conditions and for its intuitive manual guidance based on low interaction forces.