A steering wheel steering angle measurement method based on dual encoders

Abstract

The invention discloses a steering angle measurement method of a steering wheel based on a dual encoder, and the measuring mechanism is as follows: a large gear ring is meshed with two small gears with different numbers of teeth respectively, and two single-turn absolute encoders are coaxially connected with the two small gears respectively to measure the rotation angle of the two small gears; the calculation method is as follows: firstly, the angle relationship between the two small gears and the large gear ring is analyzed, and then the multi-turn value of the first encoder is assumed to obtain the multi-turn value of the second encoder, and the assumption is tested to see whether it is correct according to the multi-turn value of the second encoder until the assumption test passes, thereby obtaining the steering angle of the steering wheel, and at the same time, the monitoring of encoder faults can be realized. The method only needs to obtain the single-turn angle of the two small gears, and does not need to obtain the multi-turn value of the small gears. After power-on, no zero position calibration is required, and the absolute steering angle of the steering wheel can be calculated; it has the advantages of simple structure, easy algorithm implementation, high reliability, etc.

Description

Technical Field

[0001] The invention relates to the field of AGV control, and in particular to a steering wheel steering angle measurement method based on a dual encoder. Background Art

[0002] At present, most domestic AGV manufacturers use a steering wheel drive structure. The steering wheel refers to a modular drive wheel that integrates drive and steering functions. The steering wheel has the advantages of high integration, strong load capacity, and flexible steering. In order to obtain steering angle feedback, the steering wheel control system requires the encoder to have a multi-turn value memory function after power failure. Usually, a multi-turn absolute encoder plus a battery solution is used to achieve the power-off memory function. However, once the encoder backup battery fails, the steering zero position will be lost, which will cause the AGV to work normally. It needs to be calibrated before it can return to normal, which will bring great economic losses to the production line.

[0003] Therefore, it is necessary to provide a steering wheel steering angle measurement and calculation method that does not require a backup battery and does not require calibration after power-on, so as to achieve the purpose of reducing the system failure rate. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a steering wheel steering angle measurement method based on dual encoders, which calculates the absolute angle of the large gear ring according to the single-turn feedback values ​​of the two installed absolute encoders, thereby obtaining the steering angle of the steering wheel.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A steering wheel steering angle measurement method based on dual encoders, the steps are as follows:

[0007] Step 1, determining the functional relationship f(θ1, θ2, θ0) between the three gear angles, where θ1 is the angle value of the first pinion 102, θ2 is the angle value of the second pinion 105, and θ0 is the angle value of the large gear ring 101;

[0008] Step 2, calculate the greatest common divisor i of the speed ratio i1 and the speed ratio i2 g , the speed ratio is i1=z0 / z1, the speed ratio is i2=z0 / z2, z0 is the number of teeth of the large gear ring 101, z1 is the number of teeth of the first pinion 102, and z2 is the number of teeth of the second pinion 105; according to the greatest common divisor i g , calculate the multi-turn value range N of the first pinion 102 1min ,N 1max , N 1min 、N 1max are the minimum and maximum values ​​of the multi-turn values ​​of the first pinion, respectively;

[0009] Step 3, obtaining feedback values ​​of the first encoder 103 and the second encoder 104, and converting them into angle values ​​(θ1, θ2) of the first pinion 102 and the second pinion 105;

[0010] Step 4, by formula Calculate in, is an estimate of θ0, is an estimate of N2, and the value of N1 is from N 1min start;

[0011] Step 5, Take the remainder and determine whether the remainder is less than i g / (2·i2); if it is less than, then the current requirement is is the correct estimated value of the angle θ0 of the large gear ring (101), that is, the steering angle of the steering wheel is obtained; otherwise, N1 is increased by 1 and step 4 is repeated; if all N1 are increased to N 1max , the requirement is still not met, indicating that the first encoder 103, the second encoder 104 or the transmission mechanism is faulty;

[0012] Furthermore, the multi-turn value range (N) of the first pinion 102 in step 2 1min ,N 1max ), N 1min for Round off the value, N 1max for Round the value to the nearest integer.

[0013] Furthermore, the measurement method is implemented based on the following device:

[0014] It includes a large gear ring 101, a first pinion 102, a first encoder 103, a second encoder 104, a second pinion 105, and a slewing support 106;

[0015] The large gear ring is rigidly connected to the slewing support 106 and rotates synchronously. The first pinion 102 is meshed with the large gear ring 101. The number of teeth of the first pinion 102 is z1, the number of teeth of the large gear ring 101 is z0, and the speed ratio of the first pinion 102 is i1=z0 / z1;

[0016] The second pinion 105 is meshed with the large gear ring 101, the number of teeth of the second pinion 105 is z2, and the speed ratio of the second pinion 105 is i2=z0 / z2;

[0017] The number of teeth of the first pinion 102 and the second pinion 105 are different, and the greatest common divisor of the speed ratio i1 and the speed ratio i2 is i g ;

[0018] The first encoder 103 is coaxial with the first pinion 102 , and the first encoder 103 is a single-turn absolute encoder, and its feedback value θ1 is the angle value of the first pinion 102 ;

[0019] The second encoder 104 is coaxial with the second pinion 105 , and the second encoder 104 is a single-turn absolute encoder, and its feedback value θ2 is the angle value of the second pinion 105 ;

[0020] The large gear ring 101 can measure at most 1 / i g The absolute angle value of the circle;

[0021] The i g Satisfy i g When ≤1, the single-turn absolute angle value of the large gear ring 101 can be calculated.

[0022] Furthermore, the functional relationship between the three gear angles is

[0023] Furthermore, the values ​​of N1 and N2 cannot be directly obtained through measurement.

[0024] Beneficial Effects

[0025] In this technical solution, the encoder is a single-turn absolute encoder, and there is no need for a multi-turn encoder, so there is no need for a backup battery. The steering angle of the steering wheel can be calculated after power-on; and it is a linear relationship, the algorithm is relatively simple, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The three-dimensional structure diagram of the dual encoder in the present invention for measuring the angle of the steering wheel gear ring

[0027] Figure 2 The figure is a flow chart of the method for calculating the steering wheel steering angle in the present invention.

[0028] Reference numerals: 101 - large ring gear; 102 - first pinion gear; 103 - first encoder; 104 - second encoder; 105 - second pinion gear; 106 - slewing support. DETAILED DESCRIPTION

[0029] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0030] Example 1

[0031] The present application provides a steering wheel steering angle measurement method based on a dual encoder, and the measurement method is implemented based on the following devices:

[0032] It includes a large gear ring 101, a first pinion 102, a first encoder 103, a second encoder 104, a second pinion 105, and a slewing support 106;

[0033] The large gear ring is rigidly connected to the slewing support 106 and rotates synchronously. The first pinion 102 is meshed with the large gear ring 101. The number of teeth of the first pinion 102 is z1, the number of teeth of the large gear ring 101 is z0, and the speed ratio of the first pinion 102 is i1=z0 / z1;

[0034] The second pinion 105 is meshed with the large gear ring 101, the number of teeth of the second pinion 105 is z2, and the speed ratio of the second pinion 105 is i2=z0 / z2;

[0035] The number of teeth of the first pinion 102 and the second pinion 105 are different, and the greatest common divisor of the speed ratio i1 and the speed ratio i2 is i g The large gear ring 101 can measure up to 1 / i g The absolute angle value of the circle; g Satisfy i g When ≤1, the single-turn absolute angle value of the large gear ring 101 can be calculated.

[0036] A first pinion is installed on the steering plane of the steering wheel to mesh with the large gear ring on the slewing support, the number of teeth of the first pinion is z1, the number of teeth of the large gear ring is z0, and the speed ratio of the first pinion is i1=z0 / z1;

[0037] A second pinion is mounted on the steering plane of the steering wheel and meshes with the large gear ring. The number of teeth of the second pinion is z2, and the speed ratio of the second pinion is i2=z0 / z2;

[0038] The speed ratio i1 and the speed ratio i2 are not equal, and the greatest common multiple of the two is i g ;

[0039] The first encoder is coaxial with the first pinion, the first encoder is a single-turn absolute encoder, and its feedback value θ1 is the angle value of the first pinion;

[0040] The second encoder is coaxial with the second pinion gear, the second encoder is a single-turn absolute encoder, and its feedback value θ2 is the angle value of the second pinion gear;

[0041] The gear transmission has the relationship: Among them, N1 is the multi-turn value of the first pinion, and N2 is the multi-turn value of the second pinion. However, the encoder that records the multi-turn value is either expensive or easy to lose the multi-turn value. For the single-turn absolute value, the multi-turn value is an unknown required value.

[0042] The large gear ring can measure up to 1 / i g The absolute angle value of the circle;

[0043] The i g Satisfy i g When ≤1, the absolute angle value θ0 of a single circle of the large gear ring can be calculated, which is the steering angle of the steering wheel.

[0044] A steering wheel steering angle measurement method based on a dual encoder according to an embodiment of the present invention is as follows: Figure 1 The structure shown in the embodiment (including a large ring gear 101, a first pinion 102, a first encoder 103, a second encoder 104, a second pinion 105, and a slewing bearing 106) is installed; wherein the large ring gear 101 is rigidly connected to the slewing bearing 106 and rotates synchronously; the first gear 102 is meshed with the large gear 101; the first encoder 103 is coaxially connected to the first pinion 102 and rotates synchronously; the second gear 105 is meshed with the large gear 101; the second encoder 104 is coaxially connected to the second pinion 105 and rotates synchronously.

[0045] In this embodiment, the module of the large gear 101, the first small gear 102, and the second small gear 105 is 2.5; the number of teeth of the large gear 101 is 127; the number of teeth of the first small gear 102 is 23; the number of teeth of the second small gear 105 is 27; the first encoder 103 and the second encoder 104 are single-turn absolute encoders.

[0046] Example 2

[0047] A method for calculating a steering wheel steering angle based on a dual encoder according to an embodiment of the present invention further includes the following steps:

[0048] Step 1: Calculate the speed ratio of the first encoder and the second encoder, and calculate the greatest common divisor i of the speed ratio g , according to the greatest common divisor i g , and thus the multi-turn range of the large gear ring is calculated to be 0~1 / i g , calculate the multi-turn value range of the first pinion (N 1min ,N 1max ).

[0049] Step 2, obtain the feedback values ​​of the first encoder and the second encoder, and convert them into the angle values ​​of the first pinion and the second pinion (θ1, θ2), assuming that N1 is N 1min .

[0050] When the steering wheel angle changes, the feedback value θ1 and the feedback value θ2 will change periodically. Since it is impossible to obtain the multi-turn value of the pinion, the steering wheel angle cannot be calculated with only one feedback value. If there are two or more encoders with different speed ratios, let the feedback value θ1 be the horizontal coordinate, the feedback value θ2 be the vertical coordinate, and the steering angle of the steering wheel be the vertical coordinate θ0. The combination of the two feedback values ​​(θ1, θ2) is mapped one by one to the steering angle θ0 of the steering wheel within a period range (θ1, θ2, θ0). The period range is determined by 1 / i g Decide.

[0051] Step 3, when the multi-turn value N1 of the first pinion is different, the solution of the equation can be obtained: Each integer N1 can obtain a set of solutions

[0052] Step 5, Take the remainder and determine whether the remainder is less than i g / (2·i2); if it is less than, then the current requirement is is the estimated angle of the large gear ring, that is, the steering angle of the steering wheel; otherwise, N1 is increased by 1 and step 4 is repeated; if all N1 increases to N 1max , the requirement is still not met, indicating that the first encoder, the second encoder or the transmission mechanism is faulty.

[0053] The above description is only a preferred example of the present invention, and does not limit the implementation mode and protection scope of the present invention. Any simple modification and equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A steering wheel steering angle measurement method based on dual encoders, characterized in that: The measurement method is implemented based on the following device: It comprises a large ring gear (101), a first pinion gear (102), a first encoder (103), a second encoder (104), a second pinion gear (105), and a slewing support (106); The large gear ring is rigidly connected to the slewing support (106) and rotates synchronously; the first pinion (102) is meshed with the large gear ring (101); the number of teeth of the first pinion (102) is z1, the number of teeth of the large gear ring (101) is z0, and the speed ratio of the first pinion (102) is i1=z0 / z1; The second pinion (105) is meshed with the large gear ring (101), the number of teeth of the second pinion (105) is z2, and the speed ratio of the second pinion (105) is i2=z0 / z2; The number of teeth of the first pinion (102) and the second pinion (105) are different, and the greatest common divisor of the speed ratio i1 and the speed ratio i2 is i g ; The first encoder (103) is coaxial with the first pinion (102), the first encoder (103) is a single-turn absolute encoder, and its feedback value θ1 is the angle value of the first pinion (102); The second encoder (104) is coaxial with the second pinion (105), the second encoder (104) is a single-turn absolute encoder, and its feedback value θ2 is the angle value of the second pinion (105); The large gear ring (101) can measure at most 1 / i g The absolute angle value of the circle; The i g Satisfy i g When ≤1, the single-turn absolute angle value of the large gear ring (101) can be calculated; The method steps are as follows: Step 1, determining the functional relationship f(θ1, θ2, θ0) between the three gear angles, θ0 is the angle value of the large gear ring (101), and the functional relationship between the three gear angles is N1 is the multi-turn value of the first pinion, and N2 is the multi-turn value of the second pinion; Step 2: Calculate the greatest common divisor i of the speed ratio i1 and the speed ratio i2 g , according to the greatest common divisor i g , calculate the multi-turn value range (N) of the first pinion (102) 1min ,N 1max ), N 1min 、N 1max are the minimum and maximum values ​​of the multi-turn values ​​of the first pinion, respectively; Step 3, obtaining feedback values ​​of the first encoder (103) and the second encoder (104), and converting them into angle values ​​(θ1, θ2) of the first pinion (102) and the second pinion (105); Step 4, by formula Calculate in, is an estimate of θ0, is an estimate of N2, and N1 is taken from N 1min start; Step 5, Take the remainder and determine whether the remainder is less than i g / (2·i2); if it is less than, then the current requirement is is the correct estimated value of the angle θ0 of the large gear ring (101), that is, the steering angle of the steering wheel is obtained; otherwise, N1 is increased by 1 and step 4 is repeated; if all N1 are increased to N 1max , the requirement is still not met, indicating that the first encoder (103), the second encoder (104) or the transmission mechanism is faulty.

2. A steering wheel steering angle measurement method based on dual encoders according to claim 1, characterized in that: The multi-turn value range (N) of the first pinion (102) in step 2 1min ,N 1max ), N 1min for Round off the value, N 1max for Round the value to the nearest integer.

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