# Research on Constant Power Control Strategy of Pure Electric Excavator
## 1 Introduction  
Traditional construction machinery driven by an internal combustion engine (ICE) has shortcomings of poor emission and high energy consumption [1]. The electric construction machinery uses the electric motor (EM) as a power source, which can achieve zero emission and no pollution in the process of construction [2, 3]. However, the traditional electric excavator only uses the EM to replace the ICE and imitates the working mode of the traditional ICE-driven excavator, which does not give full play to the excellent speed regulation performance and strong overload capacity of the EM. The electric power train system has been successfully applied in the automotive field. However, there are essential differences between the excavator and automobile in terms of the transmission mode, working characteristics, and working conditions. Therefore, the control of EM in an electric excavator needs to be redesigned according to the actual requirements of the excavator. Currently, research on the electric excavator is limited [4], especially on the control of EM in an electric excavator. Some research on the EM driving technology used in hybrid power train systems has been carried out. [PERSON] et al. studied the EM applied to the energy regeneration system for a hybrid hydraulic excavator. The EM and hydraulic accumulator were used to prolong the energy regeneration time. The torque control for EM, which realized pressure compensation for the throttle valve to ensure dynamic performance, was studied [5]. [PERSON] et al. studied the power train control and energy flow management for a hybrid hydraulic excavator. The dynamic programming control method was used to optimize system parameters [6]. [PERSON] et al. studied the parameter matching method for a hybrid hydraulic excavator [7]. [PERSON] et al. applied the dynamic programming algorithm to control the powertrain system [8]. In a hybrid hydraulic excavator, even though the EM is used, the engine is still the main power unit. The EM is an auxiliary power source, which compensates the load fluctuation and stabilizes working points of ICE in a high-efficiency area. The working conditions, control method, as well as control target of the EM in the electric excavator and that of a hybrid hydraulic excavator are totally different. Therefore, the EM control mode in a hybrid power system is not suitable for a pure electric system. In an excavator, in order to ensure that the hydraulic pump can effectively absorb the power from the power source, and to avoid shutting down of the ICE in case of severe speed reduction in heavy duty [9], the power matching control strategy according to the power output characteristics of the hydraulic pump should be used. In a traditional ICE-driven excavator, due to the limited response ability of the ICE, the power matching between the power source and hydraulic pump is achieved by adjusting the working point of constant power for a variable displacement pump through a proportional reduction valve [10; 11; 12]. In a traditional electric excavator, the EM is used to replace the ICE and simulate the speed regulation of the ICE. The power matching control is generally based on a traditional hydraulic excavator, which did not give full play to its excellent speed regulation performance and strong overload capacity [13; 14; 15]. Besides, in a traditional electric excavator, the constant power setting point of the load sensing pump of the traditional pure electric drive excavator should be lower than the rated power of the EM, and there will be no system overload and shutdown failures. However, the rated power of the EM should be larger, which increases the cost of the whole machine [8; 16]. In an electric excavator, the EM is the main power source. The excellent overload capability of the EM can enable the EM to work under short-term overload, when encountering heavy duty load [17; 18; 19], and improve the maximum output power of the power train system, so as to improve the dynamic performance of the system [20; 21].