Remote steering control method and remote steering control device for wheel loader

Abstract

The embodiment of the invention provides a remote steering control method and device of a wheel loader, the wheel loader comprises a vehicle control unit, and the remote steering control method comprises the steps that first rotation angle information of a remote control end is obtained and sent to an electro-hydraulic steering valve; the electro-hydraulic steering valve controls the valve group to perform steering action; second rotation angle information of an angle sensor is obtained, the angle sensor is arranged at the hinged position of a front frame and a rear frame of the wheel loader, and the second rotation angle information is angle information between the front frame and the rear frame; under the condition that the first rotation angle information and the second rotation angle information are consistent, a signal for stopping rotation is sent to the electro-hydraulic conversion valve, and a locking signal is sent to the remote control end; by means of the remote steering control method, the problems that in remote control of the wheel loader, angle information collected during steering is inaccurate, and the signal transmission rate is low can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of wheel loaders, and more specifically, to a remote steering control method and a remote steering control device for a wheel loader. Background Art

[0002] The closed-loop feedback of the existing remote-controlled steering system is achieved by installing a steering angle sensor on the steering wheel and measuring the steering wheel rotation to feedback the steering wheel rotation angle. However, the steering angle sensor has high precision requirements and a measurement range of 360°. However, when the loader is installed on the steering wheel, it will produce large vibrations when working, resulting in unstable and deviation collected steering wheel angles, making the steering angle information collected at the remote end inaccurate. Moreover, the steering angle sensor is relatively expensive. In addition, the feedback of the steering angle sensor first passes through the steering valve and then enters the vehicle controller, with a slow transmission rate and high latency. Summary of the invention

[0003] The present application is provided to solve the above defects existing in the prior art. A remote steering control method and a remote steering control device for a wheel loader are needed to overcome the problems of inaccurate steering angle information and slow signal transmission rate during remote control of the wheel loader.

[0004] In a first aspect of the present application, a remote steering control method for a wheel loader is provided, the wheel loader comprising a vehicle controller, the remote steering control method comprising the following steps performed by the vehicle controller: obtaining first rotation angle information of a remote control end, and sending the first rotation angle information to an electro-hydraulic steering valve, so that the electro-hydraulic steering valve controls a valve group to perform a steering action; obtaining second rotation angle information of an angle sensor, the angle sensor being arranged at a hinge position of a front frame and a rear frame of the wheel loader, the second rotation angle information being angle information between the front frame and the rear frame; when the first rotation angle information and the second rotation angle information are consistent, sending a stop rotation signal to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve controls the valve group to stop the steering action; when the first rotation angle information and the second rotation angle information are consistent, sending a locking signal to the remote control end, so that the steering motor of the remote control end is locked.

[0005] According to a second aspect of the present application, a remote steering control device for a wheel loader is provided, the remote steering control device comprising a vehicle controller, the vehicle controller being configured to: obtain first rotation angle information from a remote control terminal, and send the first rotation angle information to an electro-hydraulic steering valve, so that the electro-hydraulic steering valve controls a valve group to perform a steering action; obtain second rotation angle information from an angle sensor, the angle sensor being disposed at a hinge position between a front frame and a rear frame of the wheel loader, the second rotation angle information being angle information between the front frame and the rear frame; and, when the first rotation angle information and the second rotation angle information are consistent, send a stop rotation signal to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve controls the valve group to stop the steering action.

[0006] A remote steering control method and a remote steering control device for a wheel loader provided in various embodiments of the present application, by arranging an angle sensor at the hinge position of the front frame and the rear frame of the wheel loader, can more accurately obtain the actual steering angle of the wheel loader based on the angle information between the front frame and the rear frame, thereby improving the accuracy of steering angle information collection, directly obtaining the second rotation angle information of the angle sensor, and comparing the angle information, thereby improving the signal transmission rate and processing efficiency, and issuing a stop steering action at a higher rate, thereby improving the accuracy and timeliness of actual action judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the drawings, which are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. The same reference numerals with letter suffixes or different letter suffixes may represent different instances of similar parts. The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the specification and claims, are used to illustrate the embodiments applied for. When appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0008] Figure 1 A flow chart showing a remote steering control method for a wheel loader according to an embodiment of the present application.

[0009] Figure 2 A schematic diagram showing a first relationship of an embodiment of the present application.

[0010] Figure 3 A schematic structural diagram of a remote steering control device for a wheel loader according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0011] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application is described in detail below in conjunction with the accompanying drawings and specific implementation examples. The embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation examples, but are not intended to limit the present application.

[0012] The words "first", "second" and similar words used in this application do not indicate any order, quantity or importance, but are only used to distinguish. The words "include" or "comprise" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements.

[0013] According to an embodiment of the present application, a remote steering control method for a wheel loader is provided, the wheel loader includes a vehicle controller, and the remote steering control method includes the following steps performed by the vehicle controller. In step 101, first rotation angle information of the remote control end is obtained, and the first rotation angle information is sent to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve controls the valve group to perform a steering action. The electro-hydraulic steering valve directly performs a steering action of the wheel loader according to the first rotation angle information, thereby realizing remote control of the wheel loader.

[0014] In step 102, the second rotation angle information of the angle sensor is obtained. The angle sensor is arranged at the hinge position of the front frame and the rear frame of the wheel loader. The second rotation angle information is the angle information between the front frame and the rear frame. When the wheel loader is in a steering action, the front frame and the rear frame form an angle. The angle sensor is located at the hinge position of the front frame and the rear frame, and can identify the real-time steering angle of the wheel loader in real time, and then obtain the second rotation angle information. The processor can be directly connected to the angle sensor without passing through the steering valve, and can directly obtain the second rotation angle information of the angle sensor, thereby ensuring real-time performance and improving the transmission rate.

[0015] In step 103, when the first rotation angle information and the second rotation angle information are consistent, a signal to stop the rotation is sent to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve control valve group stops the steering action. Based on the real-time second rotation angle information, it is possible to compare in real time whether the current rotation angle reaches the control angle of the remote control end. When the first rotation angle information and the second rotation angle information are consistent, it means that the control angle has been reached. At this time, sending a command to stop the steering action can timely control the actual action of the wheel loader, avoiding the inability to control the action of the wheel loader in real time and accurately due to delay. If the control angle is not reached, no stop steering command is issued.

[0016] In step 104, when the first rotation angle information and the second rotation angle information are consistent, a locking signal is sent to the remote control end to lock the steering motor of the remote control end. The remote cockpit steering gear is connected to the steering motor hardware. When the remote cockpit steering gear rotates, the steering motor rotates accordingly. When it is detected that the steering angle of the wheel loader has reached the maximum steering angle, a maximum torque current signal is sent to the steering motor to lock the steering motor and complete the closed-loop control. This can give the operator a prompt and avoid the operator from making misoperations, thereby ensuring the safety of the vehicle and driving.

[0017] Therefore, the remote steering control method of the wheel loader of the present application can make the steering angle transmitted remotely in real time the actual steering angle of the whole vehicle, overcome the angle error problem of steering wheel rotation caused by strong vibration, improve the transmission rate, and reduce the delay.

[0018] The vehicle controller may be a central controller on the wheel loader that controls the movement of the vehicle, and the central controller may include a processor, etc., to perform communication and data processing. The electro-hydraulic steering valve may be a valve group that controls the steering of the vehicle. In some embodiments, the vehicle controller sends the real-time second rotation angle information to the remote control terminal, so that the remote control personnel can obtain the rotation status in real time, thereby ensuring the safety of the vehicle and driving.

[0019] In some embodiments, the angle measurement range of the angle sensor includes -90° to 90°, the second rotation angle information output by the angle sensor is voltage information, and the angle sensor outputs voltage information according to a first relationship, wherein the first relationship includes a proportional relationship between voltage and angle. The first relationship is as follows Figure 2 As shown, the vehicle's left steering angle range is -90°~0°, and the angle sensor output voltage range is 0.5~2.5V; the vehicle's right steering angle range is 0°~90°, and the angle sensor output voltage range is 2.5~4.5V. In this way, the real-time steering angle of the wheel loader can be accurately identified. For example: the angle sensor collects the wheel loader's steering angle to reach 20°, and transmits the corresponding voltage signal 1.5V to the vehicle controller. The comparison module of the vehicle controller compares the received analog signal with the steering angle signal sent. If the steering angle control command sent remotely is 20°, the steering data sending module will issue a stop steering command; if the steering angle control command sent remotely is 30°, the steering data sending module will not issue a stop steering command, and the vehicle will continue to steer.

[0020] In some embodiments, when the electro-hydraulic steering valve receives the second rotation angle information, it verifies the second rotation angle information by means of CRC check, and parses the second rotation angle information if the verification is passed. The electro-hydraulic steering valve uses a cyclic redundancy check code to perform data verification of synchronous communication on the received second rotation angle information. When the electro-hydraulic steering valve receives the communication data of the vehicle controller of the wheel loader, the cyclic redundancy check code can improve the accuracy and normal transmission of the instruction. The electro-hydraulic steering valve can also feed back the received second rotation angle information of the vehicle controller to the vehicle controller to monitor the accuracy of the instructions of both parties, monitor the real-time signal communication status, realize the dual feedback of the angle signal and the control instruction, and increase the information accuracy of the steering control system. For example, the electro-hydraulic steering valve and the vehicle controller perform a CRC check of a cycle count of 0-15. If the check is normal, the steering instruction information 12 34 56 70 (hexadecimal code) with a steering CAN address frame of 0xFFFFFFFF is received from the vehicle controller, that is, 12 34 is a steering angle instruction frame, and 56 70 is a steering speed instruction frame, thereby controlling the on and off of the valve. At the same time, the steering command information 12 34 56 70 (hexadecimal code) is fed back to the vehicle controller through the CAN address 0xFFFF1111, thereby realizing control command feedback.

[0021] The content format of the CRC check algorithm may be HEX, and the algorithm polynomial may be x^16+x^15+x^2+1.

[0022] In some embodiments, the remote steering control method further includes: the vehicle controller performs a CRC check on the first rotation angle information after receiving the first rotation angle information. The vehicle controller first converts the analog signal into a CAN signal, and then performs a CRC check. This improves the accuracy of the received remote control command and avoids erroneous operations.

[0023] In some embodiments, the remote steering control method further includes: the vehicle controller obtains corresponding steering angle information based on the first rotation angle information through table lookup, the first rotation angle information includes output voltage information of the steering motor, and the range of the steering angle information is -90°~90°. The steering angle information in the first rotation angle information is the output voltage information of the steering motor, and the steering angle of 0-360 degrees and the steering angle of -360~0 degrees correspond to different output voltage values, respectively, and then the corresponding angle information of the front frame and the rear frame is obtained through table lookup for correspondence.

[0024] In some embodiments, the remote steering control method also includes: the remote control end controller obtains first rotation angle information based on the output voltage information of the steering motor of the remote control end, specifically including: obtaining steering direction information based on the difference in the output voltage of the steering motor, the difference in the output voltage is the current output voltage value of the steering motor and the output voltage value of the previous step; obtaining steering angle information based on the voltage value of the output voltage of the steering motor.

[0025] The remote cockpit steering gear is connected to the steering motor hardware. When the remote cockpit steering gear rotates, the steering motor rotates accordingly. The steering motor is transmitted to the remote control end controller via analog signals. The remote control end controller compares the current voltage of the steering motor with the previous voltage. If the difference is positive, it is judged as positive steering, and if the difference is negative, it is judged as negative steering.

[0026] The steering angle can be obtained based on the voltage value of the output voltage of the steering motor. The greater the angle of rotation of the remote cockpit steering gear, the greater the voltage value of the output voltage of the steering motor, and the greater the steering angle corresponding to the first rotation angle information.

[0027] In some embodiments, the first rotation angle information also includes steering angular velocity information, and the remote steering control method also includes: the remote control end controller determines the steering angular velocity information based on the voltage difference of the output voltage of the steering motor, and the voltage difference of the output voltage is the difference between the current output voltage value of the steering motor and the output voltage value of the previous step.

[0028] In some embodiments, the steering angular velocity information is determined based on the voltage difference of the output voltage of the steering motor, specifically including: determining the positive and negative of the angular velocity based on the voltage difference of the output voltage of the steering motor; converting the voltage value into an angular velocity value; determining the corresponding output angular velocity information based on the angular velocity value and the corresponding relationship, wherein the corresponding relationship includes the corresponding relationship between the output angular velocity value and the preset range threshold. If the voltage difference is positive, the angular velocity is greater than 0, and if the voltage difference is negative, the angular velocity is less than 0. The range of the angular velocity value is -300r / min~300r / min, the minimum voltage value corresponds to 0r / min, and the maximum voltage value corresponds to 300r / min, and then the angular velocity value can be converted through the corresponding relationship.

[0029] Taking the angular velocity greater than 0 as an example, the correspondence between the preset range threshold and the output angular velocity value may include: when 0 < angular velocity value < 50, the angular velocity value is constantly output at 70; when 50 < angular velocity value < 150, the angular velocity value is constantly output at 100; when 150 < angular velocity value < 270, the angular velocity value is constantly output at 200; when angular velocity value > 270, the angular velocity value is constantly output at 300. This can make the output command change smoothly and reduce the impact and fluctuation caused by steering. If the loader's command has large impact or fluctuation, it may cause large differences in action, inaccurate action output, and easy to cause work errors.

[0030] In some embodiments, when the change value of the angular velocity is greater than the first threshold value, the corresponding output angular velocity information is determined based on the angular velocity value and the corresponding relationship, and the change value of the angular velocity is the difference between the current angular velocity and the angular velocity of the previous step. For example, if the angular velocity of the previous step is 50r / min, the current angular velocity is 60r / min, and the first threshold value is 10, then the corresponding output angular velocity information is determined based on the preset range threshold value of the angular velocity value.

[0031] In some embodiments, the remote steering control method further includes: the vehicle controller obtains the corresponding opening information of the electro-hydraulic steering valve by looking up the table based on the angular velocity information in the first rotation angle information. For example, -300r / min to 300r / min, the corresponding valve opening is 0 to 100. -300r / min~0r / min, corresponding to an opening of 0 to 100. 0r / min~300r / min, corresponding to an opening of 0 to 100. The positive and negative angular velocity represents the steering direction of the electro-hydraulic steering valve. The greater the angular velocity, the greater the corresponding valve opening, so as to control the corresponding steering speed.

[0032] According to an embodiment of the present application, a remote steering control device for a wheel loader is also provided. The remote steering control device 300 includes a vehicle controller 301, and the vehicle controller 301 is configured to: obtain first rotation angle information of a remote control terminal 302, and send the first rotation angle information to an electro-hydraulic steering valve 303, so that the electro-hydraulic steering valve 303 controls the valve group to perform a steering action; obtain second rotation angle information of an angle sensor 304, wherein the angle sensor 304 is arranged at a hinge position between a front frame and a rear frame of the wheel loader, and the second rotation angle information is the angle information between the front frame and the rear frame; when the first rotation angle information and the second rotation angle information are consistent, a signal to stop rotation is sent to the electro-hydraulic steering valve 303, so that the electro-hydraulic steering valve 303 controls the valve group to stop steering action; when the first rotation angle information and the second rotation angle information are consistent, a locking signal is sent to the remote control terminal 302, so that the steering motor of the remote control terminal 302 is locked. The remote steering control device for a wheel loader of the present application can make the steering angle transmitted remotely in real time the actual steering angle of the whole vehicle, overcome the angle error problem of steering wheel rotation caused by strong vibration, increase the transmission rate, and reduce delay.

[0033] In some embodiments, the angle measurement range of the angle sensor 304 includes -90°~90°, the second rotation angle information output by the angle sensor 304 is voltage information, and the angle sensor 304 is configured to output voltage information based on a first relationship, wherein the first relationship includes a proportional relationship between voltage and angle.

[0034] In some embodiments, the electro-hydraulic steering valve 303 is configured to: upon receiving the second rotation angle information, first verify the second rotation angle information by means of CRC check, and if the verification passes, parse the second rotation angle information.

[0035] The electro-hydraulic steering valve 303 includes a first receiving module and a first sending module, and the first receiving module and the first sending module are used to communicate with the vehicle controller. The vehicle controller includes a second receiving module and a second sending module, and the second receiving module and the second sending module are used to communicate with the remote control terminal 302 and the electro-hydraulic steering valve 303.

[0036] In some embodiments, the vehicle controller is further configured to: upon receiving the first rotation angle information, perform a CRC check on the first rotation angle information.

[0037] In some embodiments, the vehicle controller is further configured to: based on the first rotation angle information, obtain the corresponding steering angle information by looking up the table, wherein the first rotation angle information includes the output voltage information of the steering motor, and the steering angle information ranges from -90° to 90°.

[0038] In some embodiments, the remote steering control device 300 also includes a remote control end controller located at the remote control end 302, and the remote control end controller is configured to: obtain first rotation angle information based on the output voltage information of the steering motor of the remote control end 302, specifically including: obtaining steering direction information based on the difference in the output voltage of the steering motor, the output voltage difference being the difference between the current output voltage value of the steering motor and the output voltage value of the previous step; obtaining steering angle information based on the voltage value of the output voltage of the steering motor.

[0039] In some embodiments, the first rotation angle information also includes steering angular velocity information, and the remote control end controller is further configured to determine the steering angular velocity information based on the voltage difference of the output voltage of the steering motor, wherein the output voltage difference is the difference between the current output voltage value of the steering motor and the output voltage value of the previous step.

[0040] In some embodiments, the steering angular velocity information is determined based on the voltage difference of the output voltage of the steering motor, specifically including: determining the positive and negative angular velocity based on the voltage difference of the output voltage of the steering motor; converting the voltage value into an angular velocity value; determining the corresponding output angular velocity information based on the angular velocity value and the corresponding relationship, wherein the corresponding relationship includes the corresponding relationship between the output angular velocity value and the preset range threshold.

[0041] In some embodiments, the vehicle controller is further configured to obtain the corresponding opening information of the electro-hydraulic steering valve 303 by looking up a table based on the angular velocity information in the first rotation angle information.

[0042] According to an embodiment of the present application, a non-transitory computer-readable medium is also provided, on which instructions are stored. When executed by a processor, the instructions execute the steps of the remote steering control method for a wheel loader as described in any embodiment of the present application. The remote steering control method for a wheel loader of the present application can make the steering angle transmitted remotely in real time the actual steering angle of the whole vehicle, overcoming the angle error problem of steering wheel rotation caused by strong vibration. The transmission rate is increased and the delay is reduced.

[0043] In addition, although exemplary embodiments have been described herein, the scope includes any and all embodiments based on the present application with equivalent elements, modifications, omissions, combinations (e.g., various embodiments intersecting schemes), adaptations or changes. The elements in the claims are to be interpreted broadly based on the language adopted in the claims, and are not limited to the examples described in this specification or during the practice of this application, and the examples are to be interpreted as non-exclusive. Therefore, this specification and examples are intended to be considered as examples only, and the true scope and spirit are indicated by the following claims and the full scope of their equivalents.

[0044] The above description is intended to be illustrative rather than restrictive. For example, the above examples (or one or more schemes thereof) may be used in combination with each other. For example, a person of ordinary skill in the art may use other embodiments when reading the above description. In addition, in the above-mentioned specific embodiments, various features may be grouped together to simplify the present application. This should not be interpreted as an intention that a feature of an application that does not require protection is necessary for any claim. On the contrary, the subject matter of the present application may be less than all the features of an embodiment of a particular application. Thus, the following claims are incorporated herein in the specific embodiments as examples or embodiments, wherein each claim is independently a separate embodiment, and it is considered that these embodiments may be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the appended claims and the full scope of equivalent forms granted by these claims.

[0045] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A remote steering control method for a wheel loader, characterized in that: The wheel loader includes a vehicle controller, and the remote steering control method includes the following steps performed by the vehicle controller: The invention relates to a method for controlling the rotation angle of the electro-hydraulic steering valve and the control device of the electro-hydraulic steering valve. The method comprises the steps of: obtaining first rotation angle information of the remote control terminal and sending the first rotation angle information to the electro-hydraulic steering valve so that the electro-hydraulic steering valve control valve group performs a steering action; obtaining second rotation angle information of an angle sensor, wherein the angle sensor is arranged at a hinge position of a front frame and a rear frame of the wheel loader, and the second rotation angle information is an angle information between the front frame and the rear frame; when the first rotation angle information and the second rotation angle information are consistent, sending a signal to stop the rotation to the electro-hydraulic steering valve so that the electro-hydraulic steering valve control valve group stops the steering action; when the first rotation angle information and the second rotation angle information are consistent, sending a locking signal to the remote control terminal so that the steering motor of the remote control terminal is locked.

2. The remote steering control method according to claim 1, characterized in that: The angle measurement range of the angle sensor includes -90° to 90°, the second rotation angle information output by the angle sensor is voltage information, and the angle sensor outputs the voltage information according to a first relationship, wherein the first relationship includes a proportional relationship between voltage and angle.

3. The remote steering control method according to claim 1, characterized in that: When the electro-hydraulic steering valve receives the second rotation angle information, it verifies the second rotation angle information by means of CRC check, and if the verification passes, it analyzes the second rotation angle information.

4. The remote steering control method according to claim 1, characterized in that: The remote steering control method also includes: the vehicle controller obtains corresponding steering angle information based on the first rotation angle information through table lookup, the first rotation angle information includes the output voltage information of the steering motor, and the range of the steering angle information is -90°~90°.

5. The remote steering control method according to claim 1, characterized in that: The first rotation angle information also includes steering angular velocity information, and the remote steering control method also includes: the remote control end controller determines the steering angular velocity information based on the voltage difference of the output voltage of the steering motor, and the voltage difference of the output voltage is the difference between the current output voltage value of the steering motor and the output voltage value of the previous step.

6. The remote steering control method according to claim 5, characterized in that: Based on the voltage difference of the output voltage of the steering motor, the steering angular velocity information is determined, specifically including: determining the positive and negative angular velocity based on the voltage difference of the output voltage of the steering motor; converting the voltage value into an angular velocity value; based on the angular velocity value and the corresponding relationship, determining the corresponding output angular velocity information, the corresponding relationship including the corresponding relationship between the output angular velocity value and the preset range threshold.

7. The remote steering control method according to claim 5, characterized in that: The vehicle controller obtains the corresponding opening information of the electro-hydraulic steering valve by looking up the table based on the steering angular velocity information in the first rotation angle information.

8. A remote steering control device for a wheel loader, characterized in that: The remote steering control device includes a vehicle controller, which is configured to: obtain first rotation angle information of the remote control end, and send the first rotation angle information to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve control valve group performs a steering action; obtain second rotation angle information of an angle sensor, the angle sensor is arranged at the hinge position of the front frame and the rear frame of the wheel loader, and the second rotation angle information is the angle information between the front frame and the rear frame; when the first rotation angle information and the second rotation angle information are consistent, send a stop rotation signal to the electro-hydraulic steering valve, so that the electro-hydraulic steering valve control valve group stops the steering action.

9. The remote steering control device according to claim 8, characterized in that: The angle measurement range of the angle sensor includes -90°~90°, the second rotation angle information output by the angle sensor is voltage information, and the angle sensor is configured to output voltage information according to a first relationship, wherein the first relationship includes a proportional relationship between voltage and angle.

10. The remote steering control device according to claim 8, characterized in that: The electro-hydraulic steering valve is configured to: upon receiving the second rotation angle information, first verify the second rotation angle information by means of CRC check, and if the verification passes, parse the second rotation angle information.

Images