# Design and Verification of a Modular Reconfigurable Test Platform for Electric Tractors
## 3 Framework Design of the Test Platform  
### Test Platform Configuration  
Based on all the topologies in Figure 1, the reconfigurable test platform consists of an internal combustion engine (ICE) system equipped with a diesel engine, an electric machine system equipped with two drive motors (DMs), a load system equipped with three load motors (LMs), a battery pack system, a transmission system, a control and measurement system, and an auxiliary system. Figure 2 presents a general schematic of the test platform. Due to the topography and population distribution characteristics of China, small and medium-power tractors are dominant in the tractor market. Therefore, the present platform was designed to meet the development test needs of electric tractors with small and medium-power. More specifically, a diesel engine with a rated power of 36.8 kW was chosen. This engine cannot only propel the load system directly or indirectly but also combine with a generator to operate as a genset that is capable of directly powering an electric powertrain and charging the battery. Drive motor 1 (DM1), and drive motor 2 (DM2) were permanent magnet synchronous machines (PMSMs) with the characteristics of high-power density, high-efficiency, and low-speed with high torque. The rated powers of the two DMs were both 22 kW. The generator (GEN) was a PMSM with a rated power of 30 kW to match the diesel engine's power. Furthermore, three asynchronous motors (AMs) with the same power (30 kW) were chosen to simulate the load system. One of them was used as the PTO load to transmit the power to the agricultural equipment like a rotary tiller, while the others imitated two rear drive wheels. The transmission system is composed mainly of a gearbox, reducer, drive axle, and power split-coupling device. In this, the power split-coupling device is vital to the architecture of the powertrain system. Moreover, the control and measurement systems are mainly composed of a dSPACE rapid prototype real-time controller and six high-precision torque-speed sensors with six corresponding torque-power instruments. Four torque-speed sensors with ranges of 500 N\(\cdot\)m and two torque-speed sensors with ranges of 200 Nm were selected to measure the torque and speed of the electric machines. In addition, to ensure that the experiment would last more than three hours, the test platform was limited to a battery pack with a size of 132 Ah. Lastly, the auxiliary system includes the cooling system and the DC charging pile. In this platform, the controllers of the two DMs and the generator use self-designed liquid cooling systems to cool down. The electric machines (including the two DMs, the generator, and the three  
Figure 2: Schematic framework of the test platform. LMs) use their own fans for air cooling. All main technical parameters of the components are displayed in Table 1.  
In this test platform, both the hardware and software were designed with a modular, reconfigurable concept. All the mechanical connections between these components are standardized and easy to install and uninstall. Moreover, the platform has enough space to install or replace the power split-coupling devices based on the different architectures of the powertrain system. The control system is also open-source and easy to expand and