Power shift axle box assembly in-loop test system and test method

Abstract

The invention discloses an in-loop test system and a test method for a power shift axle box assembly. The in-loop test system comprises the power shift axle box assembly, a driving module, a first rear axle loading module, a second rear axle loading module, a front axle loading module, a motor frequency converter group, a measurement module, a control cabinet and an upper computer, the measuring module is connected with the power gear shifting axle box assembly, the driving module, the first rear axle loading module, the second rear axle loading module, the front axle loading module, the control cabinet and the upper computer. A transmission controller is arranged on the power gear shifting bridge box assembly; the transmission controller is connected with an upper computer through a whole vehicle CAN bus. The motor frequency converter group is respectively connected with the first rear axle loading module, the second rear axle loading module, the front axle loading module and the driving module; the control cabinet is further connected with the motor frequency converter set and the upper computer. The performance and control logic verification of the transmission body and the controller under the whole vehicle working condition is realized, and the software and hardware performance test requirements of the power shifting axle box assembly under different working conditions are met.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile power system testing, and in particular relates to an in-loop testing system and a testing method for a power shift axle box assembly. Background Art

[0002] The power shift axle box assembly for tractors includes a power shift transmission and a drive rear axle. It is one of the core components of high-end high-horsepower agricultural tractors. Its shift module includes a multi-plate wet clutch and synchronizer. It executes the shift control instructions of the transmission controller (TCU) through the hydraulic system. It has the advantages of fast shifting, easy operation, a wide speed ratio range, and the ability to achieve power shifting and reversing under load.

[0003] At present, the early testing of the transmission mainly includes hardware-in-the-loop testing and bench testing. As an intelligent transmission product for high-end agricultural machinery, the power shift bridge box assembly for tractors has more complex internal mechanical structure, hydraulic system and TCU electronic control logic. It is extremely difficult to establish accurate dynamic and hydraulic system simulation models. Only simplified simulation models can be established, resulting in the limitation of in-the-loop testing due to the simplification of simulation models. Only some functional and trend verification work can be carried out. In addition, most of the existing bench tests are aimed at the function and performance testing of the transmission mechanical body, and the control logic of the TCU under the whole vehicle working conditions cannot be verified. More whole vehicle working conditions cannot be reproduced in the early testing links, which ultimately leads to a large amount of whole box calibration and verification work must be carried out on the actual vehicle. This is undoubtedly not conducive to shortening the new product development cycle and reducing R&D costs, and it is in urgent need of improvement. Summary of the invention

[0004] In response to the above technical problems, the present invention provides an in-loop testing system and testing method for a power shift axle box assembly to solve the technical problem in the prior art that it is impossible to fully verify the internal mechanical structure, hydraulic circuit and electronic control system of the transmission system while simulating the operating conditions of the entire vehicle, thereby improving the test range and test accuracy, reducing development costs, and shortening the R&D cycle.

[0005] The present invention is specifically implemented by the following technical solutions:

[0006] A power shift axle box assembly in-loop test system, comprising a loop test bench, a control cabinet and a host computer, wherein the in-loop test bench is provided with a drive module, a first rear axle loading module, a second rear axle loading module, a front axle loading module, a measurement module, a motor inverter group and a transmission controller interface;

[0007] The measuring module is respectively connected to the driving module, the first rear axle loading module, the second rear axle loading module, the front axle loading module, the control cabinet and the host computer;

[0008] The transmission controller interface is capable of performing signal interaction with the host computer;

[0009] The motor frequency converter group is respectively connected to the first rear axle loading module, the second rear axle loading module, the front axle loading module and the driving module;

[0010] The control cabinet is also connected to the motor frequency converter group and the host computer respectively.

[0011] The present invention also has the following technical features:

[0012] Specifically, the driving module includes a first DC variable frequency motor, and the first DC variable frequency motor is connected to the input shaft of the power shift bridge box assembly to be tested through a first transmission shaft.

[0013] Furthermore, the first rear axle loading module, the second rear axle loading module and the front axle loading module are respectively provided with a first speed torque sensor, a second speed torque sensor and a third speed torque sensor, and the first speed torque sensor, the second speed torque sensor and the third speed torque sensor are all connected to the measuring module.

[0014] Furthermore, the measuring module is also connected to the driving module, and a pressure sensor, a temperature sensor and a flow sensor arranged on the power shift bridge box assembly to be tested.

[0015] Furthermore, the motor inverter group includes a first inverter, a second inverter, a third inverter and a fourth inverter arranged in parallel, the first inverter is connected to the second rear axle loading module, the second inverter is connected to the front axle loading module, the third inverter is connected to the drive module, and the fourth and third inverters are connected to the first rear axle loading module.

[0016] Furthermore, the host computer includes a test bench control system and a simulation system, the test bench control system is used to exchange data with the transmission controller and the measurement module, and the simulation system is used to simulate the vehicle's operating environment and driving conditions to generate real-time target speed control signals and operating instructions.

[0017] Furthermore, the simulation system includes an engine model, a vehicle dynamics model, a road load model and a virtual cockpit model; the engine model is used to generate a target speed instruction, and send the generated target speed instruction to the drive module; the vehicle dynamics model is used to simulate the dynamic characteristics of the vehicle transmission system; the road load model is used to generate driving resistance data according to the set test operating conditions parameters, and send the generated driving resistance data to the vehicle dynamics model; the virtual cockpit model is used to generate driver operation instructions, and send the generated driver operation instructions to the transmission controller and the engine model.

[0018] The present invention also discloses a power shift axle box assembly in-loop testing method, comprising the following steps:

[0019] Step 1: Construct the vehicle dynamics model, road load model, engine model and virtual cockpit model of the power shift axle box assembly test system according to the test requirements;

[0020] Step 2: placing the power shift axle box assembly to be tested in a power shift axle box assembly test system, setting the test condition parameters, and sending the test condition parameters to the road load model and the vehicle dynamics model;

[0021] Step 3: Run the virtual cockpit model to generate a vehicle start command, and send the generated vehicle start command to the transmission controller and the engine model;

[0022] Step 4: Run the engine model to generate a target speed command, and send the generated target speed command to the drive module; the transmission controller generates a shift command, and sends the generated shift command signal to the transmission actuator;

[0023] Step 5: Run the road load model to generate dynamic load data according to the current test condition; run the vehicle dynamics model to convert the generated dynamic load data into target torque instructions for the front and rear axles; send the generated target torque instructions to the first rear axle loading module, the second rear axle loading module and the front axle loading module respectively, and the first rear axle loading module, the second rear axle loading module and the front axle loading module execute the received target torque instructions;

[0024] Step 6: The transmission controller sends an engine request speed signal to the engine model, and the engine model sends a drive module target speed command to the test bench control system. The drive module drives the power shift axle box assembly to operate according to the received target speed command.

[0025] Step 7: The host computer receives the test data and sensor information during the operation of the power shift axle box assembly, and generates the current operation status information of the power shift axle box assembly;

[0026] Step 8: judging whether the current working condition has completed the test according to the current tractor operation status information generated in step 7, if so, proceeding to step 9, if not, returning to step 4;

[0027] Step 9, determine whether to change the test condition, if so, reset the test condition parameters and return to step 2, if not, go to step 10;

[0028] Step 10: Run the virtual cockpit model to generate a shutdown command and end the test.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The system of the present invention includes a simulation system and hardware equipment that are connected and arranged. The simulation system is used to construct a vehicle dynamics model to analyze the operating status of the power shift axle box assembly. The hardware equipment is used to collect operating data of the power shift axle box assembly, and the collected operating data is fed back to the test module and then fed back to the simulation system, thereby building a closed-loop power shift axle box assembly test system. With the help of the closed-loop system, data collection, data processing, driving simulation and dynamics model simulation can be completed simultaneously, and finally a virtual-real fusion performance test of the power shift axle box assembly can be achieved. In particular, the performance and control logic of the transmission body and the controller under the whole vehicle working condition are verified, and the software and hardware performance test requirements of the power shift axle box assembly under different operating conditions are met.

[0031] (2) The method of the present invention takes the structural body of the power shift bridge box assembly and the transmission controller as the test objects, and constructs a whole vehicle environment simulation platform according to the adapted test parameters, which combines the advantages of both hardware-in-the-loop simulation and bench test, can simulate different whole vehicle working conditions to complete relevant tests, improves the simulation restoration degree and simulation accuracy, can fully verify the mechanical structure, hydraulic system and electronic control strategy of the product, and effectively solves the problems of long product actual measurement cycle, low efficiency and high cost.

[0032] Other advantages of the present invention are described in detail in the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solution of the present disclosure, the drawings required for use in the description of the embodiments of the present disclosure will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 It is the control logic diagram of the present invention. DETAILED DESCRIPTION

[0036] The following are specific embodiments of the present invention. It should be noted that, in the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "connection" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a direct connection or an indirect connection, etc. For ordinary technicians in this field, the specific meanings of the above terms in this technical solution can be understood according to specific circumstances.

[0037] The present invention is not limited to the following specific embodiments. The specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. As long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0038] Example 1

[0039] Following the above technical solution, Figure 1 As shown, this embodiment discloses an in-loop test system for a power shift axle box assembly, including an in-loop test bench, a control cabinet and a host computer, wherein a drive module, a first rear axle loading module, a second rear axle loading module, a front axle loading module, a measurement module, a motor inverter group and a transmission controller interface are arranged on the in-loop test bench; the measurement module is respectively connected to the drive module, the first rear axle loading module, the second rear axle loading module, the front axle loading module, the control cabinet and the host computer; the transmission controller interface can perform signal interaction with the host computer; the motor inverter group is respectively connected to the first rear axle loading module, the second rear axle loading module, the front axle loading module and the drive module; the control cabinet is also respectively connected to the motor inverter group and the host computer.

[0040] Among them, the drive module is used to simulate the engine to drive the gearbox in the power shift axle box assembly; the first rear axle loading module and the second rear axle loading module are both used for rear axle load simulation; the front axle loading module is used for front axle load simulation; the motor inverter group is used to realize the speed and torque control of the DC variable frequency motor in the drive module, the first rear axle loading module, the second rear axle loading module and the front axle loading module; the measurement module is used to receive the collected test data and transmit the received test data to the host computer and the control cabinet; the control cabinet is used to receive the dynamic control instructions sent by the host computer, and send the received dynamic control instructions to the first rear axle loading module, the second rear axle loading module, the front axle loading module and the drive module respectively via the motor inverter group; the host computer is used to simulate the working environment and working conditions, interact with the vehicle CAN bus for data, send the transmission controller control instructions and receive the transmission controller status information; interact with the test bench CAN bus for data and receive the data collected by all sensors.

[0041] As a preferred solution of this embodiment, the driving module includes a first DC variable frequency motor, and the first DC variable frequency motor is connected to the input shaft of the power shift bridge box assembly through a first transmission shaft.

[0042] As a preferred solution of this embodiment, the first rear axle loading module and the second rear axle loading module have the same structure, and the first rear axle loading module includes a second DC variable frequency motor, and the second DC variable frequency motor drive shaft is connected to the wheel side output shaft of the power shift bridge box assembly to be tested; the front axle loading module includes a third DC variable frequency motor drive shaft connected to the front axle output shaft of the power shift bridge box assembly.

[0043] As a preferred solution of this embodiment, the first rear axle loading module, the second rear axle loading module and the front axle loading module are respectively provided with a first speed torque sensor, a second speed torque sensor and a third speed torque sensor, and the first speed torque sensor, the second speed torque sensor and the third speed torque are all connected to the measuring module; the first speed torque sensor is used to collect the speed torque data of the wheel side on one side of the rear axle, and transmit the collected speed torque data to the measuring module; the second speed torque sensor is used to collect the speed torque data of the wheel side on the other side of the rear axle, and transmit the collected speed torque data to the measuring module; the third speed torque sensor is used to collect the speed torque data of the output shaft of the front axle, and transmit the collected speed torque data to the measuring module.

[0044] As a preferred solution of this embodiment, the measuring module can also perform signal exchange with the driving module, and the pressure sensor, temperature sensor and flow sensor arranged on the power shift bridge box assembly to be tested.

[0045] In this embodiment, a plurality of pressure sensors, temperature sensors and flow sensors are also arranged on the power shift axle box assembly to be tested, wherein the pressure sensor is installed on the corresponding pressure measuring port on the hydraulic system of the power shift axle box assembly to be tested, and is capable of collecting parameters such as pressure; the temperature sensor is installed on the power shift axle box assembly to be tested, and is used to collect the system oil temperature and the temperature of each bearing; the flow sensor is connected in series to the system circuit and lubrication circuit of the power shift axle box assembly to be tested, and is used to collect the hydraulic system flow and lubrication flow, and the pressure sensor, temperature sensor and flow sensor are all connected to the measuring module.

[0046] As a preferred scheme of this embodiment, the motor inverter group includes a first inverter, a second inverter, a third inverter and a fourth inverter arranged in parallel, the first inverter is connected to the second rear axle loading module, the second inverter is connected to the front axle loading module, the third inverter is connected to the drive module, and the fourth inverter is connected to the first rear axle loading module.

[0047] As a preferred solution of this embodiment, the host computer includes a test bench control system and a simulation system. The test bench control system is used to interact with the transmission controller and the measurement module for data. The simulation system is used to simulate the vehicle's operating environment and driving conditions to generate real-time target speed control signals and operating instructions.

[0048] The simulation system includes an engine model, a vehicle dynamics model, a road load model and a virtual cockpit model. The simulation system is used to simulate the vehicle's operating environment and working conditions to generate real-time target speed control signals and operating instructions. In this embodiment, the simulation system is built based on Matlab / simulink, where the virtual driving model is used to send simulated driving instructions to the transmission controller and the engine model to simulate the driver's driving actions under different working conditions;

[0049] The engine model is used to generate a target speed command, and send the generated target speed command to the drive module. The drive module drives the power shift axle box assembly to be tested according to the received target speed command.

[0050] The road load model is used to generate driving resistance data according to the set test condition parameters, and send the generated driving resistance data to the vehicle dynamics model to simulate the road load characteristics;

[0051] The vehicle dynamics model is used to generate the front axle / rear axle target torque and the front axle / rear axle speed, and send the generated front axle / rear axle target torque and the front axle / rear axle speed to the rear axle loading module and the front axle loading module to simulate the transmission system dynamics characteristics of the vehicle.

[0052] Preferably, the control cabinet includes hardware boards, PLC, CAN interface module, peripheral interface and UPS. The control cabinet can interact with the inverter for sending motor control instructions and receiving inverter status information; interact with the measurement module for parameter setting and status feedback of the measurement module; interact with the test bench CAN bus for receiving sensor signals as motor control feedback; and interact with the host computer for receiving host computer control instructions and sending hardware status information.

[0053] In summary, the in-loop test system for the power shift axle box assembly provided in this embodiment includes mechanical connection and communication interaction. The mechanical connection includes the connection between the input shaft, wheel-side output shaft, front axle output shaft and other mechanical parts of the power shift axle box assembly to be tested and the corresponding drive / loading module; the communication interaction is realized through the communication between the host computer and the TCU. The system provided in this embodiment builds a closed-loop power shift axle box assembly test system, uses the simulation system to build a vehicle dynamics model and the power shift axle box assembly to perform operating status analysis; uses hardware equipment to collect the operating data of the power shift axle box assembly, and feeds the collected operating data (such as pressure data, flow data, temperature data) back to the simulation system. With the help of this test system, data collection, data processing, driving simulation and dynamic model simulation are completed simultaneously, and finally the virtual-real fusion performance test of the power shift axle box assembly is realized.

[0054] Example 2

[0055] This embodiment discloses a method for testing a power shift axle box assembly in the loop. The method uses the power shift axle box assembly in the loop testing system disclosed in Example 1 for testing. The control logic during the test is as follows: Figure 2 As shown in the figure: the virtual cockpit model generates simulated signals of the driver's operation instructions, including engine start signal, accelerator pedal signal, clutch pedal signal, steering lever signal, shift signal, and working mode selection signal, wherein the engine-related signals are sent to the engine model, and the target speed signal is generated by the engine model and sent to the drive module, the drive module executes the corresponding speed instruction, and sends the gearbox-related signals to the TCU, and the TCU executes the corresponding instruction operation. At the same time, the internal status information of the TCU and the built-in sensor signal are sent to the virtual cockpit for display; by setting relevant test condition parameters, including load, slope angle, cultivated land type, number of plowshares, and plowing depth, a whole vehicle simulation test condition is constructed, and the set test condition parameters are sent to the road load model, and the road load model generates data such as the whole vehicle driving resistance, and the whole vehicle dynamics model generates target signals such as the dynamic torque, load distribution, wheel side speed difference, and front and rear speed difference of the front and rear axles of the bridge box assembly, and the test bench control system sends the above target signals to the first rear axle loading module, the second loading module, and the front axle loading module to execute relevant target instructions. During the test, the TCU will also generate a request speed signal to the engine in real time. In this test system, the engine model receives the signal and generates a target speed instruction, which is then sent by the test bench control system to the drive module to execute the dynamically changing target speed.

[0056] The test method specifically includes the following steps:

[0057] Step 1: Construct the vehicle dynamics model, road load model, engine model and virtual cockpit model of the power shift axle box assembly test system according to the test requirements;

[0058] Step 2: placing the power shift axle box assembly to be tested in a power shift axle box assembly test system, setting the test condition parameters, and sending the test condition parameters to the road load model and the vehicle dynamics model;

[0059] Step 3: Run the virtual cockpit model to generate a vehicle start command, and send the generated vehicle start command to the transmission controller and the engine model;

[0060] Step 4: Run the engine model to generate a target speed command, and send the generated target speed command to the drive module; the transmission controller generates a shift command, and sends the generated shift command signal to the transmission actuator;

[0061] Step 5: Run the road load model, generate dynamic load data according to the current test condition, run the vehicle dynamics model, convert the generated dynamic load data into target torque signals for the front and rear axles, and send the generated target torque signals to the first rear axle loading module, the second rear axle loading module, and the front axle loading module respectively; the first rear axle loading module, the second rear axle loading module, and the front axle loading module execute the received target torque signals, and in the process of engaging the starting gear, the TCU sends an engine request speed signal to the drive engine model, and the engine model realizes the change of the input motor speed by controlling the drive module, thereby completing the smooth starting action of the vehicle;

[0062] Step 6: The transmission controller sends an engine request speed signal to the engine model, and the engine model sends a drive module target speed command to the test bench control system. The drive module drives the power shift bridge box assembly to operate according to the received target speed command, and collects data through the set sensors during the operation and transmits it to the test module;

[0063] Step 7: The host computer receives the test data and sensor information during the operation of the power shift axle box assembly, and generates the current operation status information of the power shift axle box assembly;

[0064] Specifically, the data collected by the pressure sensor, speed sensor, and torque sensor can be sent to the test module, and the gear status, target vehicle speed and other information sent by the TCU can be sent to the host computer via the vehicle CAN bus. Finally, the operating status of the mechanical system, hydraulic system and electronic control system of the power shift bridge assembly can be observed on the display interface of the host computer.

[0065] Step 8: judging whether the current working condition has completed the test according to the current operating status information of the power shift axle box assembly, if so, proceeding to step 9, if not, returning to step 4;

[0066] Step 9, determine whether to change the test condition, if yes, change the test condition parameters and return to step 2, if no, go to step 10;

[0067] Step 10: Run the virtual cockpit model to generate a shutdown command and end the test.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A power shift axle box assembly in-loop test system, characterized in that: It includes an in-loop test bench, a control cabinet and a host computer, wherein the in-loop test bench is provided with a drive module, a first rear axle loading module, a second rear axle loading module, a front axle loading module, a measurement module, a motor inverter group and a transmission controller interface; The measuring module is respectively connected to the driving module, the first rear axle loading module, the second rear axle loading module, the front axle loading module, the control cabinet and the host computer; The transmission controller interface is capable of performing signal interaction with the host computer; The motor frequency converter group is respectively connected to the first rear axle loading module, the second rear axle loading module, the front axle loading module and the driving module; The control cabinet is also connected to the motor frequency converter group and the host computer respectively.

2. The power shift axle box assembly in-loop test system according to claim 1, characterized in that: The driving module comprises a first DC variable frequency motor, which is connected to an input shaft of a power shift bridge box assembly to be tested via a first transmission shaft.

3. The power shift axle box assembly in-loop test system according to claim 1, characterized in that: The first rear axle loading module, the second rear axle loading module and the front axle loading module are respectively provided with a first speed torque sensor, a second speed torque sensor and a third speed torque sensor, and the first speed torque sensor, the second speed torque sensor and the third speed torque are all connected to the measuring module.

4. The power shift axle box assembly in-loop test system according to claim 1, characterized in that: The measuring module is also connected to the driving module, and a pressure sensor, a temperature sensor and a flow sensor arranged on the power shift bridge box assembly to be measured.

5. The power shift axle box assembly in-loop test system according to claim 1, characterized in that: The motor inverter group includes a first inverter, a second inverter, a third inverter and a fourth inverter arranged in parallel, the first inverter is connected to the second rear axle loading module, the second inverter is connected to the front axle loading module, the third inverter is connected to the drive module, and the fourth inverter is connected to the first rear axle loading module.

6. The power shift axle box assembly in-loop test system according to claim 1, characterized in that: The host computer includes a test bench control system and a simulation system. The test bench control system is used to exchange data with the transmission controller and the measurement module. The simulation system is used to simulate the vehicle's operating environment and driving conditions and generate real-time target speed control signals and operating instructions.

7. The power shift axle box assembly in-loop test system according to claim 6, characterized in that: The simulation system includes an engine model, a vehicle dynamics model, a road load model and a virtual cockpit model; the engine model is used to generate a target speed instruction, and send the generated target speed instruction to a drive module; the vehicle dynamics model is used to simulate the dynamic characteristics of the vehicle's transmission system; the road load model is used to generate driving resistance data according to the set test operating condition parameters, and send the generated driving resistance data to the vehicle dynamics model; the virtual cockpit model is used to generate driver operation instructions, and send the generated driver operation instructions to a transmission controller and an engine model.

8. A power shift axle box assembly in-loop testing method, the method is implemented by using the power shift axle box assembly in-loop testing system according to any one of claims 1 to 7, comprising the following steps: Step 1: Construct the vehicle dynamics model, road load model, engine model and virtual cockpit model of the power shift axle box assembly test system according to the test requirements; Step 2: placing the power shift axle box assembly to be tested in a power shift axle box assembly test system, setting the test condition parameters, and sending the test condition parameters to the road load model and the vehicle dynamics model; Step 3: Run the virtual cockpit model to generate a vehicle start command, and send the generated vehicle start command to the transmission controller and the engine model; Step 4: Run the engine model to generate a target speed command, and send the generated target speed command to the drive module; The transmission controller generates a shift command and sends the generated shift command signal to the transmission actuator; Step 5: Run the road load model to generate dynamic load data according to the current test condition; run the vehicle dynamics model to convert the generated dynamic load data into target torque instructions for the front and rear axles; send the generated target torque instructions to the first rear axle loading module, the second rear axle loading module and the front axle loading module respectively, and the first rear axle loading module, the second rear axle loading module and the front axle loading module execute the received target torque instructions; Step 6: The transmission controller sends an engine request speed signal to the engine model, and the engine model sends a drive module target speed command to the test bench control system. The drive module drives the power shift axle box assembly to operate according to the received target speed command. Step 7: The host computer receives the test data and sensor information during the operation of the power shift axle box assembly, and generates the current operation status information of the power shift axle box assembly; Step 8: judging whether the current working condition has completed the test according to the current tractor operation status information generated in step 7, if so, proceeding to step 9, if not, returning to step 4; Step 9, determine whether to change the test condition, if yes, reset the test condition parameters and return to step 2, if no, go to step 10; Step 10: Run the virtual cockpit model to generate a shutdown command and end the test.

Images