## 1 Introduction  
Tracked vehicles are widely used in agriculture, weapons, and engineering construction because of their superior performance under complex conditions. The load simulation technology of a tracked vehicle is rapidly evolving because it can provide a convenient, effective, and lifelike test environment [1; 2; 3]. By modifying different parameters on the test bench, the power output, emission performance, and braking performance of the vehicle under different temperature, humidity, and ground conditions can be tested. Additionally, only when the body inertia and ground load simulated by the loading system are consistent with the real situation can the load simulation research test be meaningful [4; 5; 6; 7]. At present, in order to overcome the problem that the traditional mechanical simulation method has a narrow simulation range and cannot achieve stepless simulation, mostresearchers use the method of an electric motor to simulate mechanical inertia (hereinafter referred to as electrical inertia) [8; 9]. In order to realize vehicle load simulation, it is necessary to model the tested vehicle and design the control system of the bench in turn. The establishment of an accurate dynamic model is the premise to achieve accurate load simulation. When the traditional method is used to establish the dynamic model of a wheeled vehicle, the equivalent mass of translational motion is calculated by estimating the coefficient of the rotating parts of the vehicle, such as wheels and transmission systems, and the equivalent inertia of the output shaft is then obtained [10; 11]. For tracked vehicle modeling, the kinetic energy of its rotating parts and the slip rate between the vehicle and the ground are basically neglected. Because the ratio of the mass of rotating parts to the total mass of wheeled vehicles is small, the estimation error of equivalent mass is small. The revolving parts of tracked vehicles include those that account for a larger proportion of the vehicle weight, and some of them weigh up to a quarter of the vehicle weight. If the same calculation method is used as that of a wheeled vehicle, the larger error will be substituted. Therefore, the equivalent inertia of a tracked vehicle is deduced. The equivalent inertia of its rotating parts, such as the track and wheel, should be independently modeled and calculated respectively. The design goal of the control system is to achieve accurate load simulation. At present, there are many methods that can be employed to realize load simulation. Reference [12] introduces an inverse dynamic method, which uses the inverse dynamic model of the tested vehicle and test-bed system to get the simulated load. The motor controls the torque according to the load. This method is simple and commonly used. However, the inverse dynamics model is usually irregular, so it contains differential terms, which will generate noise and lead to system instability. Reference [13; 14] proposes a speed tracking method, which introduces a torque sensor to measure the output torque of the tested system, and then obtains the system speed according to the dynamic model of the system, and uses the motor to follow the target speed. This method avoids inverse dynamics. [PERSON] compares the two methods by simulation, and points out that the speed tracking method is suitable for the control scheme of a large non-linear load. Reference [15; 16] conducts a further investigation based on the study of the inverse dynamic method and speed tracking method. The system control framework is built by using a PI controller and PI estimator respectively, which aims to solve some of the drawbacks of the speed tracking method, such as the sensitivity to parameter variation, which makes it less accurate for the emulating of high-speed and high-power loads. Relevant tests on electrical vehicles and a non-linear pendulum are carried out, and good results are obtained.