Open Access

Marius Miller, Markus Pfeil, Ralph Kennel

• Bicycle-drawn cargo trailers with an electric drive to enable the transportation of high cargo loads are used as part of the last-mile logistics. Depending on the load, the total mass of a trailer can vary between approx. 50 and 250 kg, potentially more than the mass of the towing bicycle. This can result in major changes in acceleration and braking behavior of the overall system. While existing systems are designed primarily to provide sufficient power, improvements are needed in the powertrain control system in terms of driver safety and comfort. Hence, we propose a novel prototype that allows measurement of the tensile force in the drawbar which can subsequently be used to design a superior control system. In this context, a sinusoidal force input from the cyclist to the trailer according to the cadence of the cyclist is observed. The novelty of this research is to analyze whether torque impulses of the cyclist can be reduced with the help of Model Predictive Control (MPC). In addition, the powertrain of the trailer is intended to support the braking process of the system with regenerative braking. In the context of this research, a first MPC controller design is carried out and analyzed with the help of a Hardware-in-the-Loop (HIL) approach where the microcontroller of the power electronics is included as hardware to ensure the vehicle dynamics control interacts properly with the lower-level field-oriented control. The battery and motor subsystems are simulated in a Typhoon HIL 604, which is supplemented by a vehicle dynamics model of the trailer that is integrated as a Functional Mock-Up Unit (FMU). First results indicate that the MPC longitudinal dynamics controller supports the driver during acceleration, attenuates the sinusoidal oscillations and reduces the force with which the trailer pushes the bicycle during braking.