Control system and control method for long-distance continuous downhill braking in automatic driving

Abstract

The present invention discloses a control system and a control method for long-distance continuous downhill braking in automatic driving, wherein the control system comprises a battery, a DC bus, an electric brake device and a drive device; the electric brake device comprises a brake control unit and a brake resistor; the drive device comprises a variable frequency motor and a variable frequency speed regulator; the control system provided by the present invention and the control method implemented by using the control system, when an AGV is in a long-term downhill process, a PLC comprehensively judges and selects a braking mode according to the battery power, the bus DC voltage and the battery charging current; through the coordinated use of regenerative braking and energy-consuming braking, part or all of the inertial power can be stored in the battery while protecting the battery performance, thereby achieving energy saving; the brake control unit monitors the DC bus voltage in real time, controls the input and removal of the brake unit, and can achieve precise speed regulation; and the charging current and charging voltage are monitored and limited in real time, thereby ensuring the safety of battery charging.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail transport vehicles, and in particular to a control system and a control method for long-distance continuous downhill braking in automatic driving. Background Art

[0002] Self-driving cars are also called driverless cars, or AGVs for short. Self-driving cars use computer systems to achieve unmanned driving. How to accurately control the braking process is a key issue in the research of autonomous driving safety technology; unmanned AGVs are transport vehicles used for maintenance, overhaul, infrastructure and other construction departments to perform tasks, and have a large load capacity. Self-driving AGVs apply unmanned driving technology to AGVs. Therefore, how to accurately control the braking process of self-driving AGVs is an important part of ensuring the safe and smooth operation of self-driving AGVs.

[0003] At present, the commonly used braking methods of AGV are mainly divided into three categories: mechanical brake-air brake, electric brake-energy consumption brake and electric brake-regenerative brake. Among them, mechanical brake-air brake is also called mechanical brake or friction brake. Mechanical brake-air brake mainly uses compressed air as power; compressed air is supplied by the vehicle's wind source system and stops the wheel through the brake shoe; on the one hand, this braking process cannot be precisely controlled, and on the other hand, this braking process stops the wheel through friction, and the inertial power during the vehicle deceleration process is converted into heat energy, resulting in energy waste. Electric brake-DC brake is to generate a constant magnetic field through DC voltage, and the magnetic field generates a braking torque to achieve braking. The inertial power in this braking process is converted into heat energy and lost in the motor rotor through the magnetic braking torque. When the inertial power is large, it is easy to burn the motor. Therefore, this braking method is not suitable for heavy load conditions. Electric brake-energy consumption brake is the most widely used braking method. In the process of electric brake-energy consumption brake, the electric energy generated by the motor increases the bus voltage. When the bus voltage increases to the upper limit value, the brake resistor is put into use, and the inertial power is consumed by converting into the heat energy of the resistor to achieve the purpose of stable speed regulation or parking. Although this braking method can achieve the purpose of stable speed regulation or parking, it wastes a lot of electric energy. Summary of the invention

[0004] The object of the present invention is to provide a control system and a control method for long-distance continuous downhill braking in automatic driving, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a control system for long-distance continuous downhill braking in automatic driving, comprising a battery, a DC bus, an electric brake device and a drive device; the electric brake device comprises a brake control unit and a brake resistor; the drive device comprises a variable frequency motor and a variable frequency speed regulator, the battery is connected to the DC bus, the variable frequency motor and the brake resistor are respectively connected to the DC bus through a branch, the branch connected to the variable frequency motor is also connected in series with a variable frequency speed regulator, and the branch connected to the brake resistor is also connected in series with a brake control unit; the battery is provided with a BMS system; there are a number of electric brake devices, and the braking powers of the electric brake devices are different; each branch connected to the brake control unit is provided with a switch device capable of controlling the branch to be opened or disconnected, and the switch devices, the brake control units and the BMS system are all bidirectionally connected to the PLC.

[0006] As a preferred technical solution of the present invention, there are three groups of the above-mentioned electric braking equipment. The braking power of the first group of electric braking equipment is set to 20% of the AGV inertia power, the braking power of the second group of electric braking equipment is set to 50% of the AGV inertia power, and the braking power of the third group of electric braking equipment is set to 70% of the AGV inertia power.

[0007] The present invention also provides a control method for long-distance continuous downhill braking in automatic driving, the control method comprising the following steps:

[0008] Step 1: When the battery power is greater than or equal to the battery charging power protection threshold or the DC bus voltage is greater than the battery charging protection voltage threshold, all the switch devices on the three branches are opened by PLC control;

[0009] Step 2: When the battery power is less than the battery charging power protection threshold and the DC bus voltage is less than the battery charging protection voltage threshold and the battery charging current is greater than or equal to the charging current upper threshold, the PLC controls to open the two switch devices with lower braking power of the electric brake equipment and the PLC controls to close the switch device on the branch where the electric brake equipment with the highest braking power is located;

[0010] Step 3: When the battery power is less than the battery charging power protection threshold and the DC bus voltage is less than the battery charging protection voltage threshold and the battery charging current is between the charging current upper threshold and the charging current lower threshold, the PLC controls to open the switch device on the branch where the electric brake device with the lowest braking power is located and the PLC controls to close the switch devices on the branches where the remaining two electric brake devices are located;

[0011] Step 4: When the battery power is less than the battery charging power protection threshold, the DC bus voltage is less than the battery charging protection voltage threshold, and the battery charging current is less than the charging current lower threshold, the PLC controls to close the three switch devices.

[0012] As a preferred technical solution of the present invention, the battery charging capacity protection threshold is 80% to 95% of the total battery capacity.

[0013] As a preferred technical solution of the present invention, the battery charging power protection threshold is 90% of the total battery power.

[0014] As a preferred technical solution of the present invention, the battery charging protection voltage threshold is 85% to 95% of the maximum voltage of the battery.

[0015] As a preferred technical solution of the present invention, the battery charging protection voltage threshold is 95% of the maximum voltage of the battery.

[0016] As a preferred technical solution of the present invention, the upper threshold of the charging current is 100% to 115% of the rated current of the battery, and the lower threshold of the charging current is 80% to 90% of the rated current of the battery.

[0017] As a preferred technical solution of the present invention, the upper threshold of the charging current is 115% of the rated current of the battery; and the lower threshold of the charging current is 90% of the rated current of the battery.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The control system provided by the present invention and the control method implemented by using the control system, when the AGV is in the process of long-term downhill, the PLC comprehensively judges and selects the braking mode according to the battery power, bus DC voltage and battery charging current. Through the coordinated use of regenerative braking and energy-consuming braking, part or all of the inertial power can be stored inside the battery while protecting the battery performance, thereby achieving the purpose of energy saving. The braking control unit monitors the DC bus voltage in real time, controls the input and removal of the braking unit, and can achieve precise speed regulation; the charging current and charging voltage are monitored and limited in real time to ensure the safety of battery charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 It is a schematic diagram of the control system topology and energy flow in the present invention;

[0021] Attached Figure 2 It is a schematic diagram of a power circuit diagram of a control system in the present invention;

[0022] Attached Figure 3 It is a schematic diagram of a PLC controller circuit diagram and a power circuit diagram in the present invention;

[0023] Attached Figure 4 It is a flow chart of the control method in the present invention.

[0024] In the figure: 1. Battery; 2. DC bus; 3. Braking control unit; 4. Braking resistor; 5. Variable frequency motor; 6. Variable frequency speed regulator; 7. BMS system; 8. Switching device. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiment of the present application will be clearly and completely described below in conjunction with the drawings in the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work results should fall within the scope of protection of this application.

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Figure 1-4 , and describes the application in detail with reference to embodiments.

[0027] A control system for long-distance continuous downhill braking in an automatic driving system, comprising a battery 1, a DC bus 2, an electric brake device and a drive device; the battery 1 provides driving power for the AGV;

[0028] The electric braking device includes a braking control unit 3 and a braking resistor 4; the driving device includes a variable frequency motor 5 and a variable frequency speed regulator 6; the battery 1 is connected to the DC bus 2, and the variable frequency motor 5 and the braking resistor 4 are each connected to the DC bus 2 through a branch, and the branch connected to the variable frequency motor 5 is also connected in series with a variable frequency speed regulator 6, which provides electrical energy to the variable frequency motor 5 and changes the speed of the variable frequency motor 5 by changing the output power frequency.

[0029] A braking control unit 3 is also connected in series to the branch connected to the braking resistor 4. The braking control unit 3 monitors the voltage of the DC bus 2 in real time and accurately controls the speed. The braking control unit 3 is bidirectionally connected to the PLC. The PLC obtains real-time DC bus 2 voltage information by bidirectionally connecting to the braking control unit 3. The real-time DC bus 2 voltage information can be used as a judgment basis for the PLC to control the switch device 8 to open or close in real time.

[0030] The battery 1 is provided with a BMS system 7, which is called Battery Management System. It monitors the power and voltage of the battery 1, can prevent the battery 1 from excessive current or voltage, and protect the battery 1. The BMS system 7 is bidirectionally connected to the PLC. The PLC can obtain the power and voltage information of the battery 1 in real time through the bidirectional connection with the BMS system 7. The real-time power and voltage information of the battery 1 can be used as the remaining judgment basis for the PLC to control the switch device 8 to open or close in real time. The PLC selects the braking mode based on the voltage information of the DC bus 2 and the power and voltage information of the battery 1. The PLC control circuit diagram is shown in FIG. Figure 3 shown.

[0031] There are several electric brake devices, and the braking powers of the several electric brake devices are different. Each branch connected to the brake control unit 3 is provided with a switch device 8 capable of controlling the branch to be opened or disconnected. Several of the switch devices 8 are bidirectionally connected to the PLC; Figure 1 and Figure 2 As shown, in this embodiment, there are three sets of electric brake equipment and two sets of driving devices. The three branch wires connected with the electric brake equipment are respectively recorded as 1# brake unit battery connection, 2# brake unit battery connection and 3# brake unit battery connection; the braking power of the electric brake equipment on the 1# brake unit battery connection is set to 20% of the running inertia power of the AGV, the braking power of the electric brake equipment on the 2# brake unit battery connection is set to 50% of the running inertia power of the AGV, and the braking power of the electric brake equipment on the 3# brake unit battery connection is set to 70% of the running inertia power of the AGV; the running inertia power refers to the work done by the inertia force generated by the AGV due to starting, braking, acceleration and deceleration. The 1# brake unit battery connection, the 2# brake unit battery connection and the 3# brake unit battery connection are all connected with switch devices 8, which are recorded as K1, K2 and K3 respectively; K1, K2 and K3 are controlled to open or close by PLC; PLC controls the opening and closing of K1, K2 and K3 according to the real-time power, real-time voltage and real-time DC bus 2 voltage information of battery 1, and dynamically selects the braking mode.

[0032] In this embodiment, there are two groups of driving devices, and two branch wires connected to the driving devices are respectively recorded as 1# variable frequency motor battery connection and 2# variable frequency motor battery connection.

[0033] When the AGV is running normally, the driving device obtains electric energy from the battery 1 through the bus to drive the AGV to run; when the AGV is braking or going downhill, the variable frequency motor 5 is converted from a power consumption state to a power generation state, and the current generated by the variable frequency motor 5 flows into the DC bus 2, and the current in the DC bus 2 increases. In order to ensure that the motor speed is controllable, the braking unit always monitors the current and voltage in the DC bus 2.

[0034] When the current and voltage in the DC bus 2 are both higher than the threshold, the PLC controls K1, K2 and K3 to open at the same time. At this time, it is a strong energy consumption braking mode, and all the inertial power in the deceleration process is converted into heat energy and consumed in the braking resistor 4, so as to achieve the purpose of accurately controlling the deceleration and protecting the battery 1; at this time, it is a strong energy consumption braking mode, and all the inertial power in the deceleration process is converted into heat energy and consumed in the braking resistor 4. At this time, no energy is distributed to the battery 1, so although the purpose of energy storage cannot be achieved, the deceleration can be accurately controlled and the battery 1 can be protected.

[0035] When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is greater than the charging current upper threshold, the PLC controls K1 and K2 to open and K3 to close. At this time, it is a medium energy consumption braking mode, and energy consumption braking and regenerative braking work together; at this time, it is a medium energy consumption braking mode, and the inertial power during the deceleration process is consumed by the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1.

[0036] When the power of battery 1 is less than the protection threshold of battery 1 charging power and the voltage of DC bus 2 is less than the protection voltage threshold of battery 1 charging and the charging current of battery 1 is less than the upper threshold of charging current but greater than the lower threshold of charging current, PLC controls K1 to open and K3 and K2 to close. At this time, it is a weak energy consumption braking mode, and energy consumption braking and regenerative braking work together. At this time, it is a weak energy consumption braking mode. As in step 2, part of the inertial power in the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining part of the inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting battery 1, but because the braking power of this step is low, the energy stored in battery 1 is higher than that in step 2.

[0037] When the battery 1 power is less than the battery 1 charging power protection threshold, the DC bus 2 voltage is less than the battery 1 voltage protection threshold, and the battery 1 charging current is less than the charging current lower threshold, the PLC controls K1, K2 and K3 to be cut off, and only regenerative braking works. At this time, only regenerative braking works, and all energy is stored in battery 1, which can protect battery 1 and recover all energy.

[0038] like Figure 4 As shown, this embodiment also provides a control method for long-distance continuous downhill braking in automatic driving, and the control method is implemented by the control system provided by this embodiment. The control method includes the following steps:

[0039] Step 1. When the power of battery 1 is greater than or equal to the charging power protection threshold of battery 1 or the voltage of DC bus 2 is greater than the charging protection voltage threshold of battery 1, the charging power protection threshold of battery 1 is 80% of the total power of battery 1; the charging protection voltage threshold of battery 1 is 85% of the maximum voltage of battery 1; the switch devices 8 on the three branches are all opened by PLC control; this is a strong energy consumption braking mode, and the inertial power during deceleration is completely converted into heat energy and consumed in the braking resistor 4. At this time, no energy is distributed to battery 1, so although the purpose of energy storage cannot be achieved, the deceleration can be accurately controlled and the battery 1 can be protected.

[0040] Step 2: When the power of battery 1 is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is greater than or equal to the charging current upper threshold, the battery 1 charging power protection threshold is 80% of the total power of battery 1; the battery 1 charging protection voltage threshold is 85% of the maximum voltage of battery 1; the charging current upper threshold is 100% of the rated current of battery 1, the PLC controls to open the two switch devices 8 of the electric brake equipment with lower braking power and the PLC controls to close the switch device 8 on the branch where the electric brake equipment with the highest braking power is located; this is the medium energy consumption braking mode, at this time, the inertial power part of the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1.

[0041] Step 3: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is between the charging current upper threshold and the charging current lower threshold, the battery 1 charging power protection threshold is 80% of the total battery 1 power; the battery 1 charging protection voltage threshold is 85% of the highest voltage of the battery 1; the charging current upper threshold is 100% of the rated current of the battery 1, and the charging current lower threshold is 80% of the rated current of the battery 1; the PLC controls to open the switch device 8 on the branch where the electric brake device with the lowest braking power is located and the PLC controls to close the switch devices 8 on the branch where the remaining two electric brake devices are located; this is a weak energy consumption braking mode, and as in step 2, at this time, the inertial power part of the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1, but because the braking power of this step is low, the energy stored in the battery 1 is higher than that in step 2.

[0042] Step 4: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is less than the charging current lower threshold, the battery 1 charging power protection threshold is 80% of the total battery 1 power; the battery 1 charging protection voltage threshold is 85% of the maximum voltage of the battery 1; the charging current lower threshold is 80% of the rated current of the battery 1; the PLC controls to close the three switch devices 8. At this time, only regenerative braking works, and all energy is stored on the battery 1, which can protect the battery 1 and recover all energy.

[0043] The control system provided in this embodiment and the control method implemented by using the control system, when the AGV is in a long downhill process, the PLC comprehensively judges and selects the braking mode based on the battery 1 power, the bus DC voltage and the battery 1 charging current. By using regenerative braking and energy-consuming braking together, while protecting the performance of the battery 1, part or all of the inertial power can be stored inside the battery 1, thereby achieving energy saving. The braking control unit 3 monitors the DC bus 2 voltage in real time, controls the input and removal of the braking unit 3, and can achieve precise speed regulation; by real-time monitoring and limiting the charging current and charging voltage, the safety of the battery 1 charging is guaranteed.

[0044] The percentage setting of the charging protection voltage threshold and the charging power protection threshold is related to comprehensive factors such as the selected battery capacity, battery performance, inertial power of the AGV, the slope of the usage scenario, the running time, the ratio of uphill and downhill time, etc. When the percentage setting value is large, the energy consumption braking effect is weakened and the regenerative braking effect is enhanced; when the percentage setting value is small, the protection of the battery is strengthened;

[0045] The upper threshold of charging current is to protect the rechargeable battery from overheating. When charging with a continuous high current, the battery pack will heat up. The upper threshold of charging current is selected according to the performance of different batteries; the lower threshold of charging current is the critical point where energy-consuming braking exits and completely relies on regenerative braking. The lower threshold of charging current is related to comprehensive factors such as the inertial power of the AGV, the slope of the usage scenario, and the duration of downhill; when the percentage setting value is larger in the range, the energy-consuming braking effect is weakened and the regenerative braking effect is enhanced; the threshold value is set according to the specific battery selection, usage scenario, and project implementation.

[0046] Example 2

[0047] The control system for long-distance continuous downhill braking in automatic driving provided in Example 2 is exactly the same as that in Example 1 and will not be described in detail in this example.

[0048] like Figure 4As shown, this embodiment also provides a control method for long-distance continuous downhill braking in automatic driving, and the control method is implemented by the control system provided by this embodiment. The control method includes the following steps:

[0049] Step 1. When the power of battery 1 is greater than or equal to the charging power protection threshold of battery 1 or the voltage of DC bus 2 is greater than the charging protection voltage threshold of battery 1, the charging power protection threshold of battery 1 is 95% of the total power of battery 1; the charging protection voltage threshold of battery 1 is 95% of the maximum voltage of battery 1; the switch devices 8 on the three branches are all opened by PLC control; at this time, it is a strong energy consumption braking mode, and the inertial power in the deceleration process is completely converted into heat energy and consumed in the braking resistor 4. At this time, no energy is distributed to battery 1, so although the purpose of energy storage cannot be achieved, the deceleration can be accurately controlled and the battery 1 can be protected.

[0050] Step 2: When the power of battery 1 is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is greater than or equal to the charging current upper threshold, the battery 1 charging power protection threshold is 95% of the total power of battery 1; the battery 1 charging protection voltage threshold is 95% of the maximum voltage of battery 1; the charging current upper threshold is 115% of the rated current of battery 1, the PLC controls to open the two switch devices 8 of the electric brake equipment with lower braking power and the PLC controls to close the switch device 8 on the branch where the electric brake equipment with the highest braking power is located; this is the medium energy consumption braking mode, at this time, the inertial power part of the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1.

[0051] Step 3: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is between the charging current upper threshold and the charging current lower threshold, the battery 1 charging power protection threshold is 95% of the total battery 1 power; the battery 1 charging protection voltage threshold is 95% of the battery 1 maximum voltage; the charging current upper threshold is 115% of the rated current of the battery 1, and the charging current lower threshold is 90% of the rated current of the battery 1; the PLC controls to open the switch device 8 on the branch where the electric brake device with the lowest braking power is located and the PLC controls to close the switch devices 8 on the branches where the remaining two electric brake devices are located; this is a weak energy consumption braking mode, and as in step 2, the inertial power part of the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1, but because the braking power of this step is low, the energy stored in the battery 1 is higher than that in step 2.

[0052] Step 4: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is less than the charging current lower threshold, the battery 1 charging power protection threshold is 95% of the total battery 1 power; the battery 1 charging protection voltage threshold is 95% of the maximum voltage of the battery 1; the charging current lower threshold is 90% of the rated current of the battery 1; the PLC controls to close the three switch devices 8. At this time, only regenerative braking works, and all energy is stored on the battery 1, which can protect the battery 1 and recover all energy.

[0053] The control system provided in this embodiment and the control method implemented by using the control system, when the AGV is in a long downhill process, the PLC comprehensively judges and selects the braking mode based on the battery 1 power, the bus DC voltage and the battery 1 charging current. By using regenerative braking and energy-consuming braking together, while protecting the performance of the battery 1, part or all of the inertial power can be stored inside the battery 1, thereby achieving energy saving. The braking control unit 3 monitors the DC bus 2 voltage in real time, controls the input and removal of the braking unit 3, and can achieve precise speed regulation; by real-time monitoring and limiting the charging current and charging voltage, the safety of the battery 1 charging is guaranteed.

[0054] The percentage setting of the charging protection voltage threshold and the charging power protection threshold is related to comprehensive factors such as the selected battery capacity, battery performance, inertial power of the AGV, the slope of the usage scenario, the running time, the ratio of uphill and downhill time, etc. When the percentage setting value is large, the energy consumption braking effect is weakened and the regenerative braking effect is enhanced; when the percentage setting value is small, the protection of the battery is strengthened;

[0055] The upper threshold of charging current is to protect the rechargeable battery from overheating. When charging with a continuous high current, the battery pack will heat up. The upper threshold of charging current is selected according to the performance of different batteries; the lower threshold of charging current is the critical point where energy-consuming braking exits and completely relies on regenerative braking. The lower threshold of charging current is related to comprehensive factors such as the inertial power of the AGV, the slope of the usage scenario, and the duration of downhill; when the percentage setting value is larger in the range, the energy-consuming braking effect is weakened and the regenerative braking effect is enhanced; the threshold value is set according to the specific battery selection, usage scenario, and project implementation.

[0056] Example 3

[0057] The control system for long-distance continuous downhill braking in automatic driving provided in Example 3 is exactly the same as that in Example 1, and will not be described in detail in this example.

[0058] like Figure 4 As shown, this embodiment also provides a control method for long-distance continuous downhill braking in automatic driving, and the control method is implemented by the control system provided by this embodiment. The control method includes the following steps:

[0059] Step 1. When the power of battery 1 is greater than or equal to the charging power protection threshold of battery 1 or the voltage of DC bus 2 is greater than the charging protection voltage threshold of battery 1, the charging power protection threshold of battery 1 is 90% of the total power of battery 1; the charging protection voltage threshold of battery 1 is 90% of the maximum voltage of battery 1; the switch devices 8 on the three branches are all opened by PLC control; this is a strong energy consumption braking mode, and the inertial power during deceleration is completely converted into heat energy and consumed in the braking resistor 4. At this time, no energy is distributed to battery 1, so although the purpose of energy storage cannot be achieved, the deceleration can be accurately controlled and the battery 1 can be protected.

[0060] Step 2: When the power of battery 1 is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is greater than or equal to the charging current upper threshold, the battery 1 charging power protection threshold is 90% of the total power of battery 1; the battery 1 charging protection voltage threshold is 90% of the maximum voltage of battery 1; the charging current upper threshold is 110% of the rated current of battery 1, the PLC controls to open the two switch devices 8 of the electric brake equipment with lower braking power and the PLC controls to close the switch device 8 on the branch where the electric brake equipment with the highest braking power is located; this is the medium energy consumption braking mode, at this time, the inertial power part of the deceleration process is consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1.

[0061] Step 3: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is between the charging current upper threshold and the charging current lower threshold, the battery 1 charging power protection threshold is 90% of the total battery 1 power; the battery 1 charging protection voltage threshold is 90% of the battery 1 maximum voltage; the charging current upper threshold is 110% of the rated current of the battery 1, and the charging current lower threshold is 85% of the rated current of the battery 1; the PLC controls to open the switch device 8 on the branch where the electric brake device with the lowest braking power is located, and the PLC controls to close the switch devices 8 on the branch where the remaining two electric brake devices are located; this is a weak energy consumption braking mode, and as in step 2, at this time, the inertial power in the deceleration process is partially consumed through the braking resistor 4, which is called energy consumption braking, and the remaining inertial power is stored in the battery 1, which is called regenerative braking. This process realizes partial energy recovery and energy saving on the basis of protecting the battery 1, but because the braking power of this step is relatively low, the energy stored in the battery 1 is higher than that in step 2;

[0062] Step 4: When the battery 1 power is less than the battery 1 charging power protection threshold and the DC bus 2 voltage is less than the battery 1 charging protection voltage threshold and the battery 1 charging current is less than the charging current lower threshold, the battery 1 charging power protection threshold is 90% of the total battery 1 power; the battery 1 charging protection voltage threshold is 90% of the maximum voltage of the battery 1; the charging current lower threshold is 85% of the rated current of the battery 1; the PLC controls to close the three switch devices 8. At this time, only regenerative braking works, and all energy is stored on the battery 1, which can protect the battery 1 and recover all energy.

[0063] The control system provided in this embodiment and the control method implemented by using the control system, when the AGV is in a long downhill process, the PLC comprehensively judges and selects the braking mode based on the battery 1 power, the bus DC voltage and the battery 1 charging current. By using regenerative braking and energy-consuming braking together, while protecting the performance of the battery 1, part or all of the inertial power can be stored inside the battery 1, thereby achieving energy saving. The braking control unit 3 monitors the DC bus 2 voltage in real time, controls the input and removal of the braking unit 3, and can achieve precise speed regulation; by real-time monitoring and limiting the charging current and charging voltage, the safety of the battery 1 charging is guaranteed.

[0064] The percentage setting of the charging protection voltage threshold and the charging power protection threshold is related to comprehensive factors such as the selected battery capacity, battery performance, inertial power of the AGV, the slope of the usage scenario, the running time, the ratio of uphill and downhill time, etc. When the percentage setting value is large, the energy consumption braking effect is weakened and the regenerative braking effect is enhanced; when the percentage setting value is small, the protection of the battery is strengthened;

[0065] The upper threshold of charging current is to protect the rechargeable battery from overheating. When charging with a continuous high current, the battery pack will heat up. The upper threshold of charging current is selected according to the performance of different batteries; the lower threshold of charging current is the critical point where energy-consuming braking exits and completely relies on regenerative braking. The lower threshold of charging current is related to comprehensive factors such as the inertial power of the AGV, the slope of the usage scenario, and the duration of downhill; when the percentage setting value is larger in the range, the energy-consuming braking effect is weakened and the regenerative braking effect is enhanced; the threshold value is set according to the specific battery selection, usage scenario, and project implementation.

[0066] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A control system for long-distance continuous downhill braking in an automatic driving, comprising a battery (1), a DC bus (2), an electric brake device and a drive device; the electric brake device comprises a brake control unit (3) and a brake resistor (4); the drive device comprises a variable frequency motor (5) and a variable frequency speed regulator (6), the battery (1) is connected to the DC bus (2), the variable frequency motor (5) and the brake resistor (4) are each connected to the DC bus (2) through a branch, the branch connected to the variable frequency motor (5) is also connected in series with the variable frequency speed regulator (6), and the branch connected to the brake resistor (4) is also connected in series with the brake control unit (3); characterized in that The battery (1) is provided with a BMS system (7); there are a plurality of electric brake devices, and the braking powers of the plurality of electric brake devices are different; each branch connected to the brake control unit (3) is provided with a switch device (8) capable of controlling the branch to be opened or disconnected, and the plurality of switch devices (8), the plurality of brake control units (3), the plurality of variable frequency motors (5) and the BMS system (7) are bidirectionally connected to the PLC; There are three groups of electric brake devices, the braking power of the first group of electric brake devices is set to 20% of the AGV inertia power, the braking power of the second group of electric brake devices is set to 50% of the AGV inertia power, and the braking power of the third group of electric brake devices is set to 70% of the AGV inertia power; The control method comprises the following steps: Step 1: When the power level of the battery (1) is greater than or equal to the battery (1) charging power protection threshold or the DC bus (2) voltage is greater than the battery (1) charging protection voltage threshold, the switch devices (8) on the three branches are all opened by PLC control; Step 2: When the power level of the battery (1) is less than the battery (1) charging power protection threshold and the DC bus (2) voltage is less than the battery (1) charging protection voltage threshold and the battery (1) charging current is greater than or equal to the charging current upper threshold, the PLC controls to open two switch devices (8) with lower braking power of the electric brake equipment and the PLC controls to close the switch device (8) on the branch where the electric brake equipment with the highest braking power is located; Step 3: When the power of the battery (1) is less than the charging power protection threshold of the battery (1) and the voltage of the DC bus (2) is less than the charging protection voltage threshold of the battery (1) and the charging current of the battery (1) is between the upper charging current threshold and the lower charging current threshold, the PLC controls to open the switch device (8) on the branch where the electric brake device with the lowest braking power is located, and the PLC controls to close the switch devices (8) on the branches where the remaining two electric brake devices are located; Step 4: When the power of the battery (1) is less than the charging power protection threshold of the battery (1), the voltage of the DC bus (2) is less than the charging protection voltage threshold of the battery (1), and the charging current of the battery (1) is less than the charging current lower threshold, the PLC controls to close the three switch devices (8); The battery (1) charging power protection threshold is 80% to 95% of the total power of the battery (1).

2. The control method for long-distance continuous downhill braking in an automatic driving according to claim 1, characterized in that: The battery (1) charging power protection threshold is 90% of the total power of the battery (1).

3. The control method for long-distance continuous downhill braking in an automatic driving according to claim 1, characterized in that: The battery (1) charging protection voltage threshold is 85% to 95% of the maximum voltage of the battery (1).

4. The control method for long-distance continuous downhill braking in an automatic driving according to claim 3, characterized in that: The battery (1) charging protection voltage threshold is 95% of the maximum voltage of the battery (1).

5. The control method for long-distance continuous downhill braking in an automatic driving according to claim 1, characterized in that: The upper threshold of the charging current is 100% to 115% of the rated current of the battery (1), and the lower threshold of the charging current is 80% to 90% of the rated current of the battery (1).

6. The control method for long-distance continuous downhill braking in an automatic driving according to claim 5, characterized in that: The upper threshold of the charging current is 115% of the rated current of the battery (1); and the lower threshold of the charging current is 90% of the rated current of the battery (1).

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