Electric slewing precision parking assist system for excavator slewing mechanism

Abstract

This invention addresses the existing problems and shortcomings of the electric slewing mechanism of a pure electric excavator and effectively solves the problem of inaccurate parking. The invention discloses a precise parking assistance system for the electric slewing mechanism of an excavator. This system utilizes the back-pressure relief function of the relief valve to generate auxiliary braking torque. By quickly switching the reversing valve handle before reaching the target braking position, it controls the three-position, four-way proportional valve connected to the motor's oil inlet and outlet. This auxiliary braking torque is applied before the electric slewing speed drops to zero, enabling the electric slewing system to accurately stop at the target position.

Description

Technical Field

[0001] The invention belongs to the field of electric excavator driving, and in particular relates to an electric slewing precise parking assist system for an excavator upper slewing mechanism. Background Art

[0002] In recent years, energy shortages and environmental pollution have become increasingly urgent global issues. Humanity is increasingly aware of the importance of energy conservation and emission reduction. Pure electric engineering machinery with batteries as energy carriers eliminates engines and uses motors as the main drive unit. It has the advantages of high power efficiency and zero emissions and is considered to be the most ideal energy-saving and emission-reduction driving method.

[0003] In the field of construction machinery, hydraulic excavators, which use hydraulic energy as the driving force for their actuators, are the most widely used earthmoving machines. During excavation operations, traditional hydraulic excavators experience high rotational frequency and high moments of inertia. This results in a significant amount of braking energy being consumed by the hydraulic valve ports, wasting energy and causing heating in the hydraulic system and shortening component life. Recovering brake energy from high-frequency operating mechanisms with high moments of inertia is an effective measure for energy conservation and consumption reduction in excavator hydraulic systems. This high moment of inertia braking energy can be recovered by converting it into hydraulic energy, storing it in accumulators for subsequent use or directly driving hydraulic components, or by converting it into electrical energy, storing it in accumulators for subsequent use. Sinotruk Group has proposed a solution for recovering braking energy from hydraulic motors through the use of a hydraulic pump (CN101858094A); Sunward Intelligent Technology has proposed a method for recovering braking energy from a swing motor through an electric motor (CN103882901A); and Changlin Machinery has applied for a patent for converting swing braking energy into hydraulic energy and storing it in an accumulator for utilization during the next swing start (CN105545884A). Hybrid and pure electric excavators mostly use electric motors to directly drive the slewing mechanism, storing the braking kinetic energy in supercapacitors and batteries for energy recovery. Due to the excellent control performance of electric motor drive and the well-established application of energy recovery and management in storage batteries in electric vehicles, excavator manufacturers such as Hitachi Construction Machinery, Komatsu, Caterpillar, Sany Heavy Industry, Zoomlion, Sunward Intelligent Technology, and Liugong have launched test vehicles with electric slewing mechanisms since 2004.

[0004] The electric slewing system of the excavator's vehicle slewing mechanism effectively solves the problem of traditional hydraulic excavators dissipating kinetic energy at the hydraulic valve port during slewing braking. However, because the electric slewing system of the excavator's vehicle slewing mechanism uses a speed control mode, reverse speed can only be applied after the current motor speed is reduced to zero. This will result in the excavator's vehicle slewing body being unable to accurately brake and stop when it moves to the target angle, and often only stops after passing the target braking angle. This brings great inconvenience to the driver's slewing operation. Swinging operations of the vehicle slewing mechanism are the most common operating conditions of excavators, but current electric slewing systems still cannot achieve accurate and efficient parking, making electric slewing unable to operate as efficiently as traditional hydraulic slewing. This limits the rapid promotion of electric slewing technology for excavator vehicle slewing mechanisms. Summary of the Invention

[0005] This invention addresses the existing problems and shortcomings of the electric slewing mechanism of a pure electric excavator and effectively solves the problem of inaccurate parking with electric slewing. The system utilizes the back-pressure relief function of the relief valve to generate auxiliary braking torque. By quickly switching the reversing valve handle before reaching the target braking position, it controls the three-position, four-way proportional valve connected to the motor's oil inlet and outlet. This auxiliary braking torque is applied before the electric slewing speed drops to zero, enabling the electric slewing system to accurately stop at the target position.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] The electric slewing precision parking assist system for the excavator's upper slewing mechanism includes: a power battery 1, a bidirectional DC-DC inverter 2, a slewing motor 3, a slewing reducer 4, a first overflow safety valve 5, a second overflow safety valve 6, a first oil replenishment check valve 7, a second oil replenishment check valve 8, an oil replenishment tank 9, a reversing valve group 10, a left steering pilot pressure sensor 14, and a right steering pilot pressure sensor 15; further comprising: an angular displacement sensor 16, a hydraulic motor 17, a first two-position two-way solenoid valve 18, an O-type three-position four-way proportional directional reversing valve 19, a pressure sensor 20, a relief valve 21, a first slewing tank 22, a second slewing tank 23, and an auxiliary slewing controller 24; wherein the reversing valve group 10 includes: a left steering pilot valve 11, a right steering pilot valve 12, and a shuttle valve 13;

[0008] The M-side output shaft of the rotary motor 3 is connected to the rotary reducer 4, the N-side input shaft of the rotary motor 3 is connected to the hydraulic motor 17, and the rotary motor 3 is connected to the power battery 1 through the bidirectional DC-DC inverter 2;

[0009] The A oil port of the hydraulic motor 17 is connected to the C oil port of the first two-position two-way solenoid valve 18, and the B oil port of the hydraulic motor 17 is connected to the D oil port of the first two-position two-way solenoid valve 18; the C oil port of the first two-position two-way solenoid valve 18 is connected to the E oil port of the O-type function three-position four-way proportional reversing valve 19, and the D oil port of the first two-position two-way solenoid valve 18 is connected to the F oil port of the O-type function three-position four-way proportional reversing valve 19; the G oil port of the O-type function three-position four-way proportional reversing valve 19 is connected to the oil inlet of the pressure sensor 20 and the relief valve 21, the oil outlet of the relief valve 21 is connected to the first rotary oil tank 22, and the H oil port of the O-type function three-position four-way proportional reversing valve 19 is connected to the second rotary oil tank 23;

[0010] The oil port A of the hydraulic motor 17 is connected to the oil inlet of the first overflow safety valve 5, the oil port B of the hydraulic motor 17 is connected to the oil inlet of the second overflow safety valve 6, the oil port A of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 7, and the oil port B of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 8; the oil outlets of the first overflow safety valve 5 and the second overflow safety valve 6 are connected to the oil supply tank 9, and the oil inlets of the first oil-supply check valve 7 and the second oil-supply check valve 8 are connected to the oil supply tank 9;

[0011] The left steering pilot valve 11 and the right steering pilot valve 12 are powered by the pilot power source PG and unloaded through the unloading oil port T when not in the switching state. The left steering pilot pressure sensor 14 and the left steering pilot valve 11 are both connected to the X1 port of the shuttle valve 13. The right steering pilot pressure sensor 15 and the right steering pilot valve 12 are both connected to the X2 port of the shuttle valve 13. The SH port of the shuttle valve 13 outputs pilot pressure oil in the steering state.

[0012] The auxiliary rotation controller 24 is connected to the feedback signal lines of the angular displacement sensor 16, the pressure sensor 20, the left steering pilot pressure sensor 14, and the right steering pilot pressure sensor 15. The auxiliary rotation controller 24 is also connected to the control signal lines of the first two-position two-way solenoid valve 18, the O-type three-position four-way proportional reversing valve 19, and the bidirectional DC-DC inverter 2.

[0013] The reversing valve group 10 sends a steering signal. When the output pressure of the left steering pilot pressure sensor 14 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn left. When the output pressure of the right steering pilot pressure sensor 15 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn right.

[0014] The relief valve 21 provides back pressure for the auxiliary braking of the hydraulic motor 17. The pressure sensor 20 monitors the back pressure of the relief valve 21. The hydraulic motor 17 provides auxiliary braking torque for the electric swing system. The angular displacement sensor 16 detects the rotation angle of the output shaft of the swing reducer 4 and sends it to the auxiliary swing controller 24. The auxiliary swing controller 24 realizes auxiliary braking of the electric swing system by controlling the O-type three-position four-way proportional reversing valve 19.

[0015] The slewing motor 3 serves as the main driving device to provide driving and braking torque for the slewing system; when the electric slewing motor of the excavator's upper slewing mechanism is in the braking condition, the O-type function three-position four-way proportional reversing valve 19 is quickly switched in advance, and the auxiliary braking torque is applied in advance to the slewing shaft connected in series with it, so that the electric slewing device stops rotating at the target position, ensuring precise parking at the target position and emergency parking in special circumstances.

[0016] The present invention has the following beneficial effects:

[0017] 1) The present invention can enable the electric slewing device of the vehicle slewing mechanism of a pure electric excavator to accurately stop at a target position.

[0018] 2) The present invention can assist the electric slewing device of the vehicle slewing mechanism of a pure electric excavator to stop in an emergency under special circumstances. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the system principle of Example 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the system principle of Example 2 of the present invention.

[0021] In the figure, 1-power battery, 2-bidirectional DC-DC inverter, 3-rotating motor, 4-rotating reducer, 5-I overflow safety valve, 6-II overflow safety valve, 7-I oil supply check valve, 8-II oil supply check valve, 9-oil supply tank, 10-reversing valve group, 11-left steering pilot valve, 12-right steering pilot valve, 13-shuttle valve, 14-left steering pilot pressure sensor, 15-right steering pilot pressure sensor Sensor, 16-angular displacement sensor, 17-hydraulic motor, 18-first two-position two-way solenoid valve, 19-O-type function three-position four-way proportional reversing valve, 20-pressure sensor, 21-overflow valve, 22-first rotary oil tank, 23-second rotary oil tank, 24-auxiliary rotary controller, 25-second two-position two-way solenoid valve, 26-third two-position two-way solenoid valve, 27-Y-type function three-position four-way proportional reversing valve. DETAILED DESCRIPTION

[0022] The following describes the detailed technical solution of the present invention in conjunction with the accompanying drawings:

[0023] Example 1

[0024] like Figure 1 As shown, the electric slewing precision parking assist system for the excavator upper vehicle slewing mechanism includes: a power battery 1, a bidirectional DC-DC inverter 2, a slewing motor 3, a slewing reducer 4, a first overflow safety valve 5, a second overflow safety valve 6, a first oil replenishment check valve 7, a second oil replenishment check valve 8, an oil replenishment tank 9, a reversing valve group 10, a left steering pilot pressure sensor 14, and a right steering pilot pressure sensor 15; further comprising: an angular displacement sensor 16, a hydraulic motor 17, a first two-position two-way solenoid valve 18, an O-type three-position four-way proportional reversing valve 19, a pressure sensor 20, a relief valve 21, a first slewing tank 22, a second slewing tank 23, and an auxiliary slewing controller 24; wherein the reversing valve group 10 includes: a left steering pilot valve 11, a right steering pilot valve 12, and a shuttle valve 13;

[0025] The M-side output shaft of the rotary motor 3 is connected to the rotary reducer 4, the N-side input shaft of the rotary motor 3 is connected to the hydraulic motor 17, and the rotary motor 3 is connected to the power battery 1 through the bidirectional DC-DC inverter 2;

[0026] The A oil port of the hydraulic motor 17 is connected to the C oil port of the first two-position two-way solenoid valve 18, and the B oil port of the hydraulic motor 17 is connected to the D oil port of the first two-position two-way solenoid valve 18; the C oil port of the first two-position two-way solenoid valve 18 is connected to the E oil port of the O-type function three-position four-way proportional reversing valve 19, and the D oil port of the first two-position two-way solenoid valve 18 is connected to the F oil port of the O-type function three-position four-way proportional reversing valve 19; the G oil port of the O-type function three-position four-way proportional reversing valve 19 is connected to the oil inlet of the pressure sensor 20 and the relief valve 21, the oil outlet of the relief valve 21 is connected to the first rotary oil tank 22, and the H oil port of the O-type function three-position four-way proportional reversing valve 19 is connected to the second rotary oil tank 23;

[0027] The oil port A of the hydraulic motor 17 is connected to the oil inlet of the first overflow safety valve 5, the oil port B of the hydraulic motor 17 is connected to the oil inlet of the second overflow safety valve 6, the oil port A of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 7, and the oil port B of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 8; the oil outlets of the first overflow safety valve 5 and the second overflow safety valve 6 are connected to the oil supply tank 9, and the oil inlets of the first oil-supply check valve 7 and the second oil-supply check valve 8 are connected to the oil supply tank 9;

[0028] The left steering pilot valve 11 and the right steering pilot valve 12 are powered by the pilot power source PG and unloaded through the unloading oil port T when not in the switching state. The left steering pilot pressure sensor 14 and the left steering pilot valve 11 are both connected to the X1 port of the shuttle valve 13. The right steering pilot pressure sensor 15 and the right steering pilot valve 12 are both connected to the X2 port of the shuttle valve 13. The SH port of the shuttle valve 13 outputs pilot pressure oil in the steering state.

[0029] The auxiliary rotation controller 24 is connected to the feedback signal lines of the angular displacement sensor 16, the pressure sensor 20, the left steering pilot pressure sensor 14, and the right steering pilot pressure sensor 15. The auxiliary rotation controller 24 is also connected to the control signal lines of the first two-position two-way solenoid valve 18, the O-type three-position four-way proportional reversing valve 19, and the bidirectional DC-DC inverter 2.

[0030] The reversing valve group 10 sends a steering signal. When the output pressure of the left steering pilot pressure sensor 14 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn left. When the output pressure of the right steering pilot pressure sensor 15 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn right.

[0031] The relief valve 21 provides back pressure for the auxiliary braking of the hydraulic motor 17. The pressure sensor 20 monitors the back pressure of the relief valve 21. The hydraulic motor 17 provides auxiliary braking torque for the electric swing system. The angular displacement sensor 16 detects the rotation angle of the output shaft of the swing reducer 4 and sends it to the auxiliary swing controller 24. The auxiliary swing controller 24 realizes auxiliary braking of the electric swing system by controlling the O-type three-position four-way proportional reversing valve 19.

[0032] The slewing motor 3 serves as the main driving device to provide driving and braking torque for the slewing system; when the electric slewing motor of the excavator's upper slewing mechanism is in the braking condition, the O-type function three-position four-way proportional reversing valve 19 is quickly switched in advance, and the auxiliary braking torque is applied in advance to the slewing shaft connected in series with it, so that the electric slewing device stops rotating at the target position, ensuring precise parking at the target position and emergency parking in special circumstances.

[0033] Example 2

[0034] like Figure 2As shown, the electric slewing precision parking assist system for the excavator upper vehicle slewing mechanism includes: a power battery 1, a bidirectional DC-DC inverter 2, a slewing motor 3, a slewing reducer 4, a first overflow safety valve 5, a second overflow safety valve 6, a first oil replenishment check valve 7, a second oil replenishment check valve 8, an oil replenishment tank 9, a reversing valve group 10, a left steering pilot pressure sensor 14, a right steering pilot pressure sensor 15; and also includes: an angular displacement sensor 16, a hydraulic motor 17, a pressure sensor 20, a relief valve 21 ... The rotary oil tank 22, the second rotary oil tank 23, the auxiliary rotary controller 24, the second two-position two-way solenoid valve 25, the third two-position two-way solenoid valve 26, and the Y-shaped three-position four-way proportional reversing valve 27. The reversing valve assembly 10 includes a left steering pilot valve 11, a right steering pilot valve 12, and a shuttle valve 13. The M-side output shaft of the rotary motor 3 is connected to the rotary reducer 4, and the N-side input shaft of the rotary motor 3 is connected to the hydraulic motor 17. The rotary motor 3 is connected to the power battery 1 via a bidirectional DC-DC inverter 2.

[0035] The A oil port of the hydraulic motor 17 is connected to the C oil port of the II two-position two-way solenoid valve 25, and the B oil port of the hydraulic motor 17 is connected to the K oil port of the III two-position two-way solenoid valve 26; the D oil port of the II two-position two-way solenoid valve 25 is connected to the E oil port of the Y-type function three-position four-way proportional reversing valve 27, and the J oil port of the III two-position two-way solenoid valve 26 is connected to the F oil port of the Y-type function three-position four-way proportional reversing valve 27; the G oil port of the Y-type function three-position four-way proportional reversing valve 27 is connected to the oil inlet of the pressure sensor 20 and the relief valve 21, the oil outlet of the relief valve 21 is connected to the I rotary oil tank 22, and the H oil port of the Y-type function three-position four-way proportional reversing valve 27 is connected to the II rotary oil tank 23;

[0036] The oil port A of the hydraulic motor 17 is connected to the oil inlet of the first overflow safety valve 5, the oil port B of the hydraulic motor 17 is connected to the oil inlet of the second overflow safety valve 6, the oil port A of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 7, and the oil port B of the hydraulic motor 17 is connected to the oil outlet of the first oil-supply check valve 8; the oil outlets of the first overflow safety valve 5 and the second overflow safety valve 6 are connected to the oil supply tank 9, and the oil inlets of the first oil-supply check valve 7 and the second oil-supply check valve 8 are connected to the oil supply tank 9;

[0037] The left steering pilot valve 11 and the right steering pilot valve 12 are powered by the pilot power source PG and unloaded through the unloading oil port T when not in the switching state. The left steering pilot pressure sensor 14 and the left steering pilot valve 11 are both connected to the X1 port of the shuttle valve 13. The right steering pilot pressure sensor 15 and the right steering pilot valve 12 are both connected to the X2 port of the shuttle valve 13. The SH port of the shuttle valve 13 outputs pilot pressure oil in the steering state.

[0038] The auxiliary rotation controller 24 is connected to the feedback signal lines of the angular displacement sensor 16, the pressure sensor 20, the left steering pilot pressure sensor 14, and the right steering pilot pressure sensor 15. The auxiliary rotation controller 24 is also connected to the control signal lines of the second two-position two-way solenoid valve 25, the third two-position two-way solenoid valve 26, the Y-type three-position four-way proportional reversing valve 27, and the bidirectional DC-DC inverter 2.

[0039] The reversing valve group 10 sends a steering signal. When the output pressure of the left steering pilot pressure sensor 14 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn left. When the output pressure of the right steering pilot pressure sensor 15 reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller 24 controls the boarding slewing mechanism to turn right.

[0040] The relief valve 21 provides back pressure for the auxiliary braking of the hydraulic motor 17. The pressure sensor 20 monitors the back pressure of the relief valve 21. The hydraulic motor 17 provides auxiliary braking torque for the electric swing system. The angular displacement sensor 16 detects the rotation angle of the output shaft of the swing reducer 4 and sends it to the auxiliary swing controller 24. The auxiliary swing controller 24 realizes auxiliary braking of the electric swing system by controlling the Y-type three-position four-way proportional reversing valve 27.

[0041] The slewing motor 3 serves as the main driving device to provide driving and braking torque for the slewing system; when the electric slewing motor of the excavator's upper slewing mechanism is in the braking condition, the Y-type three-position four-way proportional reversing valve 27 is quickly switched in advance, and the auxiliary braking torque is applied in advance to the slewing shaft connected in series with it, so that the electric slewing device stops rotating at the target position, ensuring precise parking at the target position and emergency parking in special circumstances.

Claims

1. The electric slewing precision parking assist system for the excavator's upper slewing mechanism includes: A power battery (1), a bidirectional DC-DC inverter (2), a rotary motor (3), a rotary reducer (4), a first overflow safety valve (5), a second overflow safety valve (6), a first oil supply check valve (7), a second oil supply check valve (8), an oil supply tank (9), a reversing valve group (10), a left steering pilot pressure sensor (14), and a right steering pilot pressure sensor (15); characterized in that it also includes: an angular displacement sensor (16), a hydraulic motor (17), a first two-position two-way solenoid valve (18), an O-type three-position four-way proportional reversing valve (19), a pressure sensor (20), a relief valve (21), a first rotary oil tank (22), a second rotary oil tank (23), and an auxiliary rotary controller (24); wherein the reversing valve group (10) includes: a left steering pilot valve (11), a right steering pilot valve (12), and a shuttle valve (13); The M-side output shaft of the rotary motor (3) is connected to the rotary reducer (4), the N-side input shaft of the rotary motor (3) is connected to the hydraulic motor (17), and the rotary motor (3) is connected to the power battery (1) via a bidirectional DC-DC inverter (2); The A oil port of the hydraulic motor (17) is connected to the C oil port of the first two-position two-way solenoid valve (18), and the B oil port of the hydraulic motor (17) is connected to the D oil port of the first two-position two-way solenoid valve (18); the C oil port of the first two-position two-way solenoid valve (18) is connected to the E oil port of the O-type function three-position four-way proportional reversing valve (19), and the D oil port of the first two-position two-way solenoid valve (18) is connected to the F oil port of the O-type function three-position four-way proportional reversing valve (19); the G oil port of the O-type function three-position four-way proportional reversing valve (19) is connected to the oil inlet of the pressure sensor (20) and the relief valve (21), the oil outlet of the relief valve (21) is connected to the first rotary oil tank (22), and the H oil port of the O-type function three-position four-way proportional reversing valve (19) is connected to the second rotary oil tank (23); The oil port A of the hydraulic motor (17) is connected to the oil inlet of the first overflow safety valve (5), the oil port B of the hydraulic motor (17) is connected to the oil inlet of the second overflow safety valve (6), the oil port A of the hydraulic motor (17) is connected to the oil outlet of the first oil replenishment check valve (7), and the oil port B of the hydraulic motor (17) is connected to the oil outlet of the first oil replenishment check valve (7); the oil outlets of the first overflow safety valve (5) and the second overflow safety valve (6) are connected to the oil replenishment tank (9), and the oil inlets of the first oil replenishment check valve (7) and the second oil replenishment check valve (8) are connected to the oil replenishment tank (9); The left steering pilot valve (11) and the right steering pilot valve (12) are powered by the pilot power source PG and unloaded through the unloading oil port T in the non-reversing state; the left steering pilot pressure sensor (14) and the left steering pilot valve (11) are both connected to the X1 port of the shuttle valve (13); the right steering pilot pressure sensor (15) and the right steering pilot valve (12) are both connected to the X2 port of the shuttle valve (13); the SH port of the shuttle valve (13) outputs the pilot pressure oil in the steering state; The auxiliary rotation controller (24) is respectively connected to the feedback signal lines of the angular displacement sensor (16), the pressure sensor (20), the left steering pilot pressure sensor (14) and the right steering pilot pressure sensor (15); the auxiliary rotation controller (24) is respectively connected to the control signal lines of the first two-position two-way solenoid valve (18), the O-type three-position four-way proportional reversing valve (19) and the bidirectional DC-DC inverter (2); The reversing valve group (10) sends a steering signal. When the output pressure of the left steering pilot pressure sensor (14) reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller (24) controls the boarding vehicle rotation mechanism to turn left. When the output pressure of the right steering pilot pressure sensor (15) reaches the pressure of the pilot pressure source PG, the auxiliary rotation controller (24) controls the boarding vehicle rotation mechanism to turn right. The overflow valve (21) provides back pressure for auxiliary braking of the hydraulic motor (17). The pressure sensor (20) monitors the back pressure of the overflow valve (21). The hydraulic motor (17) provides auxiliary braking torque for the electric rotary system. The angular displacement sensor (16) detects the rotation angle of the output shaft of the rotary reducer (4) and sends it to the auxiliary rotary controller (24). The auxiliary rotary controller (24) realizes auxiliary braking of the electric rotary system by controlling the O-type three-position four-way proportional reversing valve (19). The slewing motor (3) serves as the main driving device to provide driving and braking torque for the slewing system; when the electric slewing motor of the excavator upper slewing mechanism is in a braking state, the O-type function three-position four-way proportional reversing valve (19) is quickly switched in advance, and the auxiliary braking torque is applied in advance to the slewing shaft connected in series with the electric slewing device to stop rotating at the target position, thereby ensuring accurate parking at the target position and emergency parking in special circumstances.

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