A rack stroke self-learning method and rack end protection method

Abstract

The present invention provides a rack stroke self-learning method and a rack end protection method, wherein the rack stroke self-learning method introduces a virtual rack total stroke, and when the actual rack stroke on one side is greater than the virtual rack limit, adjusts the virtual rack limit on that side and converts the virtual rack limit on the other side through the virtual rack total stroke, so that the converted virtual rack limit can always fall within the actual rack total stroke, thereby avoiding the defect that the actual rack limit on one side cannot be learned after being less than the virtual rack limit due to excessive rack assembly deviation. The rack end protection method of the present invention introduces a protection position ratio. The smaller the protection position ratio, the smaller the speed-type protection torque. As the current position of the rack enters the trigger angle range and gradually approaches the virtual rack limit, the value of the protection position ratio is closer to the value "1", thereby making the speed-type protection torque change smoother and avoiding the phenomenon of jamming during operation.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile power steering, and in particular to a rack stroke self-learning method and a rack end protection method. Background Art

[0002] In electric power steering systems without rack end-of-travel protection, rapid and violent impacts of the rack at the end of mechanical travel can damage the mechanical block. Furthermore, traditional rack end-of-travel protection, due to the fixed rack travel, can weaken or even fail to provide protection when the rack is deformed by impact.

[0003] When the steering wheel is turned quickly, the rack end protection torque can increase with the speed, quickly playing a damping effect to protect the rack from damage. Patent No. CN105644617B discloses a rack end protection method. Once either end of the rack enters any protection area, the power-assist torque output by the electric power steering system is reduced, and the reduction in the power-assist torque is proportional to the distance between the end of the rack entering the protection area and the starting point of the protection area, and the reduction related to the distance is recorded as F1; and is also proportional to the rack displacement speed, and the reduction in the displacement speed is recorded as F2. The reduction in the power-assist torque is the sum of F1 and F2. After the displacement speed is introduced into this method, when the rack enters the protection area and the rack is at a speed that is too high, the power-assist torque will suddenly decrease a lot, and there will be a jamming phenomenon during operation, affecting driving comfort.

[0004] Existing rack travel self-learning methods are primarily used to match software and hardware when assembling new vehicles. The system's initial virtual rack limits are set to be smaller than the actual rack limits. Once the vehicle is assembled, this method allows the system to learn and match the actual rack limits. For example, patent number CN106915381 discloses a maximum steering angle self-learning method for an electric power steering system. When the steering wheel's left turn angle exceeds a default calibrated left limit angle value, the current steering wheel angle value is recorded. When the steering wheel returns to within a steering wheel update position threshold, the recorded steering wheel angle value is used as the left limit angle calibration update value. The steering wheel update position threshold: When the steering wheel returns to this position, the left and right steering wheel limit angle values ​​are updated. When the steering wheel's right turn angle exceeds a default calibrated right limit angle value, the current steering wheel angle value is recorded. When the steering wheel returns to within the steering wheel update position threshold, the recorded steering wheel angle value is used as the right limit angle calibration update value. The defect of this method is that it can only learn values ​​greater than the virtual rack limit, that is, when the actual rack limit is greater than the virtual rack limit, the system updates the virtual rack limit to the larger actual rack limit; during normal assembly, the left and right virtual limits are smaller than the actual virtual limits, but when the rack assembly has a large deviation, the virtual limit at one end is smaller than the actual limit, while the virtual limit at the other end may be larger than the actual limit. This is because the patented and existing technologies cannot make the large virtual limit learn to the smaller actual limit, so that the virtual rack limit is greater than the actual rack limit. When the rack end protection method is running, the actual protection range is reduced, so that the protection torque at the rack limit is reduced relative to the required protection torque, thereby reducing the protection strength of the rack end and failing to better protect the rack end. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a rack stroke self-learning method and a rack end protection method. When the rack assembly deviation is large, the virtual limit can be updated to a smaller actual limit value; in addition, the phenomenon of jamming during operation when the rack enters the protection area, that is, the trigger angle range, is avoided.

[0006] A rack stroke self-learning method, characterized by comprising the following steps:

[0007] Step 1: Set the virtual rack stroke smaller than the rack design stroke;

[0008] Step 2: Set the zero point where the virtual rack travel D1 and the actual rack travel coincide;

[0009] Step 3: When the actual measurement value S1 of one side is greater than the virtual limit R0, the virtual limit R0 of the side is updated to the actual measurement value S1, recorded as R2, and step 4 is executed; otherwise, step 3 is executed;

[0010] Step 4: Subtract R2 from the virtual rack stroke D1 to obtain a calculated virtual limit C0; update the virtual limit L0 on the other side to the calculated virtual limit C0, which is recorded as L1;

[0011] Step 5: When the actual measurement value S2 on the other side is greater than L1, update L1 to the actual measurement value S2, denoted as L2, and execute step 6; otherwise, execute step 7;

[0012] Step 6: Take the sum of R2 and L2 as the new virtual rack stroke D1 and jump to step 3;

[0013] Step 7: When the actual measurement value S1 of one side is greater than the virtual limit R0, update the virtual limit R0 of the side to the actual measurement value S1, recorded as R2, and jump to the step 4; otherwise, jump to the step 5.

[0014] Further: Step 2 specifically includes setting the angle value corresponding to the moment on the actual rack stroke and the virtual rack stroke to zero when the vehicle is moving straight.

[0015] Further, step 6 further includes, after verifying the zero points of the actual rack stroke and the virtual rack stroke, jumping to step 3.

[0016] A rack end protection method, characterized by comprising the following steps:

[0017] Step 1: Obtain the distance S11 that the rack enters the trigger angle range. The position protection torque is proportional to the distance S11.

[0018] Step 2: Divide the distance the rack enters the trigger angle range by the trigger angle range to obtain the protection position ratio;

[0019] Step 3: The speed-type protection torque is proportional to the product of the protection position ratio and the rack speed;

[0020] Step 4: The rack end protection torque is the sum of the position protection torque and the speed protection torque;

[0021] Step 5: The amount of reduction in the power-assistance torque output by the electric power steering system is the rack end protection torque.

[0022] Further: the step 1 includes,

[0023] Step 1.1: Obtain R2 and L2 from the rack travel self-learning method;

[0024] Step 1.2: Get the current position of the rack S12;

[0025] Step 1.3: Subtract the trigger angle range from the virtual limit R2 or L2 on the side corresponding to the current rack position to obtain the difference S13;

[0026] Step 1.4: When S12 is greater than S13, the distance S11 that the rack enters the trigger angle range is equal to S12 minus S13.

[0027] Beneficial effects of the present invention: The rack stroke self-learning method of the present invention introduces a virtual rack total stroke, and when the actual rack stroke on one side is greater than the virtual rack limit, the virtual rack limit on that side is adjusted and the virtual rack limit on the other side is converted by the virtual rack total stroke. Since the virtual rack total stroke is less than the actual rack total stroke, the converted virtual rack limit can always fall within the actual rack total stroke, thereby avoiding the defect that the actual rack limit on one side cannot be learned after being less than the virtual rack limit due to excessive rack assembly deviation; in addition, in the rack stroke self-learning method, when the virtual rack limits on both sides are less than the actual rack limits, this learning method can also learn the actual rack limits simply and quickly. The rack end protection method of the present invention introduces a protection position ratio. The smaller the protection position ratio, the smaller the speed-type protection torque. As the current position of the rack enters the trigger angle range and gradually approaches the virtual rack limit, the value of the protection position ratio is closer to the value "1", thereby making the speed-type protection torque change smoother and avoiding the phenomenon of jamming during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the positional relationship between the virtual rack stroke and the actual rack stroke after the rack is assembled in the rack stroke self-learning method;

[0029] Figure 2 This is a schematic diagram of the positional relationship between the virtual rack stroke and the actual rack stroke after the rack is assembled in the rack stroke self-learning method;

[0030] Figure 3 This is the logic flow chart of the rack stroke self-learning method. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the accompanying drawings.

[0032] A rack stroke self-learning method, characterized by comprising the following steps:

[0033] Step 1: Set a virtual rack stroke that is smaller than the rack design stroke. Generally, the single-side limit of the virtual rack stroke is 5-15° smaller than the rack design stroke. Of course, this value is just the inventor's personal design habit. This range can be expanded or reduced without special requirements.

[0034] Step 2: Set the zero point where the virtual rack travel D1 and the actual rack travel coincide. When the vehicle is traveling straight, set the angle between the actual rack travel and the virtual rack travel at that moment to zero.

[0035] Step 3: When the actual measurement value S1 on the left side (or the right side) is greater than the virtual limit R0, the virtual limit R0 on that side is updated to the actual measurement value S1, recorded as R2, and step 4 is executed; otherwise, step 3 is executed;

[0036] Step 4: Subtract R2 from the virtual rack stroke D1 to obtain a calculated virtual limit C0; update the right (or left) virtual limit L0 to the calculated virtual limit C0, which is recorded as L1;

[0037] Step 5: When the actual measurement value S2 on the right side (or the left side) is greater than L1, update L1 to the actual measurement value S2, denoted as L2, and execute step 6; otherwise, execute step 7;

[0038] Step 6: Take the sum of R2 and L2 as the new virtual rack stroke D1 and jump to step 3;

[0039] Step 7: When the actual measurement value S1 on the left side (or the right side) is greater than the virtual limit R0, update the virtual limit R0 of this side to the actual measurement value S1, recorded as R2, and jump to step 4; otherwise, jump to step 5.

[0040] Alternatively, step 6 may be performed by using the sum of R2 and L2 as the new virtual rack travel D1, verifying the zero points of the actual rack travel and the virtual rack travel, and then, when the virtual limit changes, verifying the zero point and jumping to step 3. The principle for replacing the contents within brackets in steps 1 to 5 is that when one is replaced, the contents within the other brackets are replaced simultaneously; otherwise, no replacement is made.

[0041] The working principle of the rack stroke self-learning method of the present invention: combined with Figure 1 As shown in the figure, when the rack assembly deviation is small, the left and right limits of the virtual rack stroke B are both smaller than the left and right limits of the actual rack stroke A; when the stroke on one side of the actual rack stroke exceeds the unilateral limit of the virtual rack stroke, the limit value on the other side of the virtual rack stroke is converted and reduced, and then when the stroke on the other side of the actual rack stroke is greater than the converted virtual rack limit, the virtual limit value is increased to the unilateral stroke, thereby expanding the virtual rack limit. At the same time, the virtual rack stroke becomes larger and approaches the actual rack stroke in this cycle.

[0042] like Figure 2As shown, when the rack assembly deviation is large, the left limit of the actual rack stroke A is greater than the left limit of the virtual rack stroke B, and the right limit of the actual rack stroke A is less than the right limit of the virtual rack stroke B; when it is detected that the left limit of the actual rack stroke A is greater than the left limit of the virtual rack stroke B, since the virtual rack stroke is less than the actual rack stroke, the left limit of the virtual rack converted by the virtual rack stroke must be within the left limit of the actual rack stroke, and the left limit of the virtual rack is updated to the actual left limit of the actual rack that is greater than it through testing.

[0043] A rack end protection method, characterized by comprising the following steps:

[0044] Step 1: Obtain the distance S11 that the rack enters the trigger angle range. The position protection torque is proportional to the distance S11.

[0045] Step 2: Divide the distance the rack enters the trigger angle range by the trigger angle range to obtain the protection position ratio;

[0046] Step 3: The speed-type protection torque is proportional to the product of the protection position ratio and the rack speed;

[0047] Step 4: The rack end protection torque is the sum of the position protection torque and the speed protection torque;

[0048] Step 5: The amount of reduction in the power-assistance torque output by the electric power steering system is the rack end protection torque.

[0049] Further: the step 1 includes,

[0050] Step 1.1: Obtain R2 and L2 from the rack travel self-learning method;

[0051] Step 1.2: Get the current position of the rack S12;

[0052] Step 1.3: Subtract the trigger angle range from the virtual limit R2 or L2 on the side corresponding to the current position of the rack to obtain the difference S13;

[0053] Step 1.4: When S12 is greater than S13, the distance S11 that the rack enters the trigger angle range is equal to S12 minus S13.

[0054] Substitute the specific data into the rack end protection method for calculation and set the following data:

[0055] Current position of rack: 530°

[0056] Virtual rack one-side limit: 540°

[0057] Trigger angle range: 30°

[0058] The proportional coefficient of the position protection torque and the distance S11 is: 1

[0059] The proportional coefficient of the speed protection torque to the product of the protection position ratio and the rack speed is: 3

[0060] Rack speed: 6.28° / s

[0061] Stroke adaptive module output: R2 or L2 = 540°

[0062] Distance S11 = 530°-(540°- 30°)=20°

[0063] Protection position ratio: 20° / 30°=0.67

[0064] Position protection torque: 20*1=20

[0065] Speed ​​protection torque: 0.67*6.28*3=12.62

[0066] The rack end protection torque is: 20+12.62=32.62Nm

[0067] Assuming the original motor assist torque is 56 Nm, after the rack end protection function is introduced, according to the above example output of 32.62 Nm, the final motor assist torque output is: 56-32.62=23.38 Nm.

[0068] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A rack stroke self-learning method, characterized by: The following steps are involved: Step 1: Set the virtual rack stroke smaller than the rack design stroke; Step 2: Set the zero point where the virtual rack travel D1 and the actual rack travel coincide; Step 3: When the actual measurement value S1 on one side is greater than the virtual limit R0, the virtual limit R0 on that side is updated to the actual measurement value S1, recorded as R2, and step 4 is executed; Otherwise, go to step 3; Step 4: Subtract R2 from the virtual rack stroke D1 to obtain a calculated virtual limit C0; update the virtual limit L0 on the other side to the calculated virtual limit C0, which is recorded as L1; Step 5: When the actual measurement value S2 on the other side is greater than L1, L1 is updated to the actual measurement value S2, recorded as L2, and step 6 is executed; Otherwise, go to step 7; Step 6: Take the sum of R2 and L2 as the new virtual rack stroke D1 and jump to step 3; Step 7: When the actual measurement value S1 of one side is greater than the virtual limit R0, update the virtual limit R0 of the side to the actual measurement value S1, recorded as R2, and jump to the step 4; otherwise, jump to the step 5.

2. A rack stroke self-learning method according to claim 1, characterized in that: The step 2 specifically includes setting the angle values ​​corresponding to the moment on the actual rack travel and the virtual rack travel to zero when the vehicle is traveling straight.

3. The rack stroke self-learning method according to claim 1, characterized in that: The step 6 further includes, after verifying the zero points of the actual rack stroke and the virtual rack stroke, jumping to the step 3.

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