A power assistance output and control method of a commercial vehicle electro-hydraulic power steering system

Abstract

The application discloses a power assistance output and control method of a commercial vehicle electric hydraulic power steering system and belongs to the technical field of automobile steer-by-wire. The application provides a working mode of the power assistance output of the commercial vehicle electric hydraulic power steering system, including a standby mode, a manual power assistance mode, an automatic power assistance mode, a superimposed torque mode, an intervention mode, a warning mode and an error mode, different power assistance outputs of the commercial vehicle electric hydraulic power steering system under different use conditions can be realized, and smooth conversion of different power assistance modes can be realized. The technical scheme provided by the application can meet the requirements of commercial vehicle steering comfort and user driving road feeling, different power assistance modes can meet different vehicle system requirements, and the automatic driving requirement of L2 level can be supported.

Description

Technical Field

[0001] This invention belongs to the field of automotive steer-by-wire technology, specifically relating to the power steering output and control method of an electro-hydraulic power steering system for commercial vehicles. Background Technology

[0002] The electro-hydraulic power steering (EHPS) control system includes a steering wheel, torque angle sensor, steering controller (ECU), brushless DC motor, worm gear reducer, recirculating ball hydraulic steering gear, and VCU. The EHPS system works by the ECU calculating the appropriate motor torque in real time based on vehicle speed, torque angle, and other signals. A PID controller then adjusts the motor to achieve the target torque, thereby driving the hydraulic steering gear to output different torques to steer the wheels. EHPS is a modification of traditional hydraulic resistance steering systems, adding a motor and ECU; therefore, existing systems can be reused with relatively minor modifications.

[0003] Compared to traditional hydraulic power steering (HPS), electro-hydraulic power steering (EHPS) can adjust the power assist in real time, saving engine energy. EHPS can be controlled in real time via software, effectively improving vehicle steering characteristics and handling stability, enhancing driver safety and comfort, and reconciling the conflict between the need for light steering at low speeds and the need for road feel at high speeds. Compared to electric power steering (EPS), EHPS offers better feel, smoother assistance, and greater power assist, making it more suitable for commercial vehicles. Therefore, there is an urgent need for a power assist output control method suitable for commercial vehicles based on electro-hydraulic power steering systems. Summary of the Invention

[0004] This invention addresses the problems of heavy and uncomfortable steering systems in traditional commercial vehicles. Based on the application scenarios of electro-hydraulic power steering systems in commercial vehicles, it proposes a method for power steering output and control of electro-hydraulic power steering systems in commercial vehicles.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A power steering system for commercial vehicles provides power steering output, including the following operating modes:

[0007] Standby mode is the first state after the steering gear is powered on, with zero output assist torque. After the steering gear self-tests, it enters manual assist mode.

[0008] Manual power steering mode is used for manual steering wheel operation. After the steering system detects the hand torque, it calculates and outputs manual power steering torque based on the vehicle speed and motor speed.

[0009] Automatic power steering mode is used when the steering system detects that the vehicle has sent a command to enter automatic power steering mode, and under the conditions of automatic power steering mode, it receives the target steering wheel angle and target angular velocity signals from the vehicle, and obtains and outputs automatic power steering torque through closed-loop control.

[0010] The superimposed torque mode is used in manual power steering mode. When the vehicle detects a risk of deviating from the lane, it sends a short superimposed torque to the steering system and outputs the superimposed torque plus the manual power steering torque.

[0011] Intervention mode is used when the steering system detects that the vehicle has sent an instruction to enter intervention mode or that the conditions for manual intervention are met in automatic power steering mode. In this case, the steering system enters intervention mode and outputs manual power steering torque.

[0012] Warning mode: When the steering system detects a warning signal, it enters warning mode and only outputs manual assist torque.

[0013] Error mode is used when the steering system detects an error signal and enters error mode, outputting zero assist torque.

[0014] The manual assist torque is obtained by subtracting the return-to-center control torque from the basic assist torque, subtracting the damping control torque, and adding the friction compensation torque and the inertia compensation torque.

[0015] The automatic power assist mode must meet all of the following conditions and last for more than 0.5 seconds: vehicle speed less than or equal to the threshold of 60 km / h; hand torque less than or equal to the threshold of 1 Nm.

[0016] The closed-loop control is specifically as follows: The P-phase control torque is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by a P-phase setting parameter. Similarly, the I-phase control torque is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by an I-phase setting parameter and then by the program running cycle. Both the P-phase and I-phase setting parameters are obtained by looking up a two-dimensional table based on the difference between the target angular velocity and the actual angular velocity; the two-dimensional table is calibrated using empirical values. The P-phase control torque and the I-phase control torque are added together to output the control motor action, causing the steering wheel to reach the target angular velocity. Simultaneously, based on the difference between the target angle and the actual angle, when the difference is greater than 50 degrees, the motor action is controlled according to the target angular velocity; when the difference is less than or equal to 50 degrees, the motor action is controlled according to the target angular velocity obtained by looking up a data table based on the difference between the target angle and the actual angle. The data table is set such that the smaller the difference between the actual angle and the target angle, the slower the target angular velocity, and the larger the difference, the faster the target angular velocity.

[0017] The vehicle is at risk of deviating from its lane, including anti-tilt control, stability control, lane departure assist, crosswind compensation, or detection of driver fatigue.

[0018] The conditions for manual intervention are: the absolute value of the manual torque signal exceeds 1 Nm and lasts for more than 0.5 s.

[0019] The warning signal is triggered when any of the following conditions are met and last for more than 0.5s: CAN message loss signal is triggered; external request target angle unavailable signal is triggered; VCU status abnormal signal is triggered; target angle absolute value is greater than 1224 degrees; target angular velocity signal absolute value is greater than 600 degrees / second; vehicle speed is greater than 150km / h; 7. Steering gear internal warning fault signal is triggered.

[0020] The error signal indicates a failure to properly control the power steering, including steering sensor malfunction, chip malfunction, or motor malfunction.

[0021] The assist torque, manual assist torque, and automatic output torque are all motor target torques after temperature compensation and torque limiting processing.

[0022] Based on the above-described control method for the power steering output of an electro-hydraulic power steering system for commercial vehicles, the conversion relationship between the various operating modes is as follows:

[0023] The standby mode is entered after the steering system starts working, and the manual power steering mode is entered after the self-test is completed.

[0024] If a warning signal is generated but no error signal is generated in standby mode, manual assist mode, automatic assist mode, superimposed torque mode, and intervention mode, then the system will enter warning mode.

[0025] If an error signal is generated in standby mode, manual assist mode, automatic assist mode, superimposed torque mode, intervention mode, and warning mode, the system will enter error mode.

[0026] In warning mode, if no warning signal or error signal is generated, it will enter standby mode.

[0027] In error mode, if no warning signal or error signal is generated, it enters standby mode; if a warning signal is generated but no error signal is generated, it enters warning mode.

[0028] In standby mode, if a signal from the vehicle requesting automatic power steering is received and the conditions for entering automatic power steering are met, then automatic power steering mode is entered; if a signal from the vehicle requesting superimposed torque mode is received, then superimposed torque mode is entered; if a signal from the vehicle requesting standby mode is received, then standby mode is entered.

[0029] In automatic power steering mode, if a request for manual power steering is received from the vehicle, the system will enter manual power steering mode; if a request for torque boosting mode is received from the vehicle, the system will enter torque boosting mode; if a request for warning mode is received from the vehicle or the manual intervention conditions are met, the system will enter warning mode.

[0030] In superimposed torque mode, if a request for manual power assist mode is received from the vehicle, the system will enter manual power assist mode; if a request for automatic power assist mode is received from the vehicle and the conditions for entering automatic power assist mode are met, the system will enter automatic power assist mode.

[0031] In intervention mode, if a request for manual power assist is received from the vehicle, the manual power assist mode will be entered.

[0032] Standby mode can be entered by the vehicle itself.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention enables commercial vehicle electro-hydraulic power steering to generate different power outputs under various operating conditions and smoothly switch between different power assist modes. Furthermore, it can promptly switch to an abnormal mode in case of abnormal situations to prevent damage to the steering system. In manual power assist mode, the power assist output completely follows the driver's feel, meeting the needs of light steering at low speeds and heavy steering at high speeds. The return-to-center function also meets active return-to-center requirements, and the damping function prevents vehicle deviation at high speeds. In automatic power assist mode, the steering system can be automatically controlled according to vehicle requests, supporting L2 level autonomous driving requirements such as automatic parking, lane centering, and traction control. The superimposed torque mode supports lane departure warning or driver fatigue warning. The intervention mode allows the driver to quickly take over in case of abnormal situations during autonomous driving. This invention satisfies the steering comfort needs of commercial vehicles and the user's requirements for road feel, and the different power assist modes can also meet the needs of different vehicle systems. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below:

[0036] Figure 1 This is a schematic diagram illustrating the switching between the power steering output working modes of the commercial vehicle electro-hydraulic power steering system of the present invention;

[0037] Figure 2 This is a schematic diagram of the software module of the steering gear in the commercial vehicle electro-hydraulic power steering system of the present invention;

[0038] Figure 3 This is a schematic diagram of an electro-hydraulic power steering system. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings:

[0040] like Figure 1 As shown, the present invention provides a power steering output and control method for an electric hydraulic power steering system for commercial vehicles, which can realize the conversion of multiple power steering working modes.

[0041] First, let's introduce the several working modes of the power steering output of this commercial vehicle's electro-hydraulic power steering system:

[0042] Standby mode, mode 0, is the first state after the steering ECU is powered on. The output assist torque is 0, the steering system performs a self-test, and after the self-test is completed, it defaults to manual assist mode.

[0043] Manual power steering mode, mode 1, is used for manual steering wheel operation. The steering system detects the hand torque and calculates the output manual power steering torque by combining information such as vehicle speed and motor speed. The manual power steering torque is obtained by subtracting the return control torque and damping control torque from the basic power steering torque, and adding the friction compensation torque and inertia compensation torque.

[0044] In Automatic Assist Mode 2, the system receives the target steering wheel angle and target angular velocity signals from the vehicle and then uses closed-loop control to obtain and output the automatic assist torque. Specifically, the closed-loop control works as follows: The P-term control torque is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by a P-term set parameter. The P-term set parameters are derived from a two-dimensional table (based on empirical values) used to calibrate the difference between the target angular velocity and the actual angular velocity. Similarly, the I-term control torque is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by an I-term set parameter and then by the program's running cycle. The I-term set parameter is also based on the target angular velocity... The target angular velocity difference is obtained by referring to a two-dimensional table, which is calibrated using empirical values. The P-phase control torque and I-phase control torque are added together to output the control motor, causing the steering wheel to reach the target angular velocity. Simultaneously, based on the difference between the target angle and the actual angle, the motor is controlled according to the target angular velocity when the difference is greater than 50 degrees; when the difference is less than or equal to 50 degrees, the target angular velocity is obtained by referring to a table based on the difference between the target angle and the actual angle. This table is set such that the closer the actual angle is to the target angle (i.e., the smaller the difference), the slower the target angular velocity; the larger the difference, the faster the target angular velocity. The closed-loop control accuracy is improved by calibrating the setting parameters of the P-phase and I-phase. Entering automatic power steering mode requires all of the following conditions to be met and maintained for more than 0.5 seconds: 1. Vehicle speed less than or equal to the threshold of 60 km / h; 2. Hand torque less than or equal to the threshold of 1 Nm.

[0045] Superimposed torque mode, mode 3, is used in manual power steering mode when the vehicle is at risk of deviating from the lane under conditions such as anti-tilt control, stability control, lane departure assist or crosswind compensation, or when driver fatigue is detected. It can send a short superimposed torque to the steering system and output the superimposed torque plus the manual power steering torque.

[0046] Intervention mode, mode 4, is used when the automatic power steering system detects that the vehicle has sent an intervention mode command or the manual intervention conditions are met. The steering system then enters intervention mode and the power steering torque output after entering intervention mode is the manual power steering torque. The manual intervention conditions are: the absolute value of the manual torque signal exceeds 1 Nm and lasts for more than 0.5 s.

[0047] Warning mode, mode 5, is used when the steering system detects a warning signal and enters warning mode. In warning mode, the output power assist torque is the manual power assist torque. A warning signal is triggered when the automatic power assist torque calculation is abnormal but does not affect the manual power assist torque calculation. A warning signal will be issued if any of the following conditions are met and last for more than 0.5 seconds: 1. CAN message loss signal activated; 2. External request target angle unavailable signal activated; 3. VCU status abnormality signal activated; 4. Target angle absolute value greater than 1224 degrees; 5. Target angular velocity signal absolute value greater than 600 degrees / second; 6. Vehicle speed greater than 150 km / h; 7. Steering system internal warning fault signal activated.

[0048] Error mode, mode 6, is activated when the steering system detects an error signal. In this mode, the power steering torque output is zero. Error signals include situations where the steering system power steering control cannot function properly, such as steering system sensor malfunction, chip malfunction, or motor malfunction.

[0049] In the above working mode, the values ​​of all limiting conditions can be calibrated, and under other constraints, all changes in the values ​​are within the scope of protection of the claims of this invention.

[0050] The conversion relationships between the various working modes mentioned above are as follows:

[0051] Mode 0, the standby mode, is entered after the steering system's ECU starts working. After the self-test is completed, it enters the default working mode, namely Mode 1, the manual power steering mode.

[0052] If a warning signal is generated but no error signal is generated in mode 0, mode 1, mode 2, mode 3 or mode 4, then mode 5 is entered.

[0053] If an error signal is generated in mode 0, mode 1, mode 2, mode 3, mode 4 or mode 5, then mode 6 will be entered.

[0054] In mode 5, if no warning signal or error signal is generated, then mode 1 is entered.

[0055] In mode 6, if no warning signal or error signal is generated, it enters mode 1; if a warning signal is generated but no error signal is generated, it enters mode 5.

[0056] In mode 1, if a vehicle requests mode 2 and the conditions for entering automatic power steering are met, then mode 2 is entered; if a vehicle requests mode 3, then mode 3 is entered; if a vehicle requests mode 0, then mode 0 is entered.

[0057] In mode 2, if a vehicle request is received, mode 1 is entered; if a vehicle request is received, mode 3 is entered; if a vehicle request is received, mode 5 is entered or the manual intervention condition is met, mode 5 is entered.

[0058] If a vehicle requests mode 1 in mode 3, then mode 1 is entered; if a vehicle requests mode 2 and the conditions for entering automatic power steering are met, then mode 2 is entered.

[0059] In mode 4, if a whole vehicle request is received, mode 1 will be entered.

[0060] Standby mode can also be entered by the vehicle itself requesting it.

[0061] The operating mode of the steering system will be sent to the entire vehicle in real time.

[0062] like Figure 3 As shown, in the electro-hydraulic power steering control system, the steering controller and VCU communicate via CAN. The steering controller receives signals from and sends signals to the VCU. The steering controller converts the final calculated power assist torque output into a motor control signal and sends it to the steering motor. Based on the conversion relationship between various operating modes, manual power assist mode is the default operating mode. After the steering system's ECU starts working, it defaults to manual power assist mode. Then, based on the real-time received vehicle signal status and the internal steering system signal status, it determines which mode to enter. Once in that mode, the corresponding power assist torque is obtained, such as... Figure 2 As shown, the assist torque, after temperature compensation and torque limiting processing, becomes the final target torque for the motor. The final target torque for the motor is then sent to the motor control mode for execution. This invention does not involve motor control.

[0063] Example

[0064] A method for controlling the power steering output of an electro-hydraulic power steering system for commercial vehicles includes the following switching of operating modes:

[0065] After the steering controller is powered on, it enters mode 0 standby mode and performs a self-test on the steering system. At this time, the steering output torque is 0. If an error signal is generated during the self-test, it enters error mode; if a warning signal is generated but no error signal is generated, it enters warning mode; if neither a warning signal nor an error signal is generated, it defaults to manual power assist mode.

[0066] In Mode 1, the manual assist torque output is calculated based on the hand torque combined with information such as vehicle speed and motor speed. If an error signal is generated, it enters error mode; if a warning signal is generated but no error signal is generated, it enters warning mode. If there are no abnormal signals, and there is an autonomous driving-related need, such as lane keeping or automatic parking being triggered, the steering system, after receiving the vehicle's request and meeting the conditions for entering automatic assist mode, will enter Mode 2 automatic assist mode.

[0067] In Mode 2, after receiving the target steering wheel angle and target angular velocity signals, the automatic power assist torque is obtained through closed-loop control. If an error signal is generated, the system enters error mode; if a warning signal is generated but no error signal is generated, the system enters warning mode. If no abnormal signal is generated, manual intervention occurs, and the absolute value of the manual torque exceeds a certain threshold of 1 Nm (calibrable) and lasts for a certain period of 0.5 s (calibrable), or the vehicle requests Mode 4, then the system enters intervention mode.

[0068] In Mode 4, the output torque is the manual power assist torque calculated based on hand torque combined with information such as vehicle speed and motor speed. If an error signal is generated, the system enters error mode; if a warning signal is generated but no error signal is generated, the system enters warning mode. If there are no abnormal signals, and the vehicle requests to enter Mode 1, the system enters automatic power assist mode.

[0069] In mode 1, if there is no abnormal signal, and a vehicle requests to enter mode 3, then the superimposed torque mode will be entered.

[0070] In Mode 3, the output torque is the manual assist torque plus the superimposed torque. If an error signal is generated, the system enters error mode; if a warning signal is generated but no error signal is generated, the system enters warning mode. If there is no abnormal signal, and a vehicle requests to enter Mode 1, the system enters manual assist mode; if a vehicle requests to enter Mode 2 and the conditions for entering automatic assist mode are met, the system enters automatic assist mode.

[0071] In Mode 5, the output torque is the manual assist torque, and automatic driving is not possible. If an error signal is generated, the system will enter error mode; if there is no error signal or warning signal, it will enter manual assist mode.

[0072] In Mode 6, the output torque is 0, and the steering system cannot provide power assist. In this mode, if a warning signal is generated instead of an error signal, it enters warning mode; otherwise, it enters manual power assist mode.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A boost output of an electric hydraulic power assisted steering system of a commercial vehicle, characterized in that The following working modes are included: Standby mode is the first state after the steering gear is powered on, with zero output power torque. After the steering gear self-tests, it enters manual power assist mode. Manual power steering mode is used for manual steering wheel operation. After the steering system detects the hand torque, it calculates the output manual power steering torque based on the vehicle speed and motor speed. Automatic power steering mode is used when the steering system detects that the vehicle has sent a command to enter automatic power steering mode, and under the conditions of automatic power steering mode, it receives the target steering wheel angle and target angular velocity signals from the vehicle, and obtains and outputs the automatic power steering torque through closed-loop control. The superimposed torque mode is used in manual power steering mode. When the vehicle detects a risk of deviating from the lane, it sends a short superimposed torque to the steering system and outputs the superimposed torque plus the manual power steering torque. Intervention mode is used when the steering system detects that the vehicle has sent an intervention mode command or the conditions for manual intervention are met in automatic power steering mode. In this mode, the steering system enters intervention mode and outputs manual power steering torque. Warning mode: When the steering system detects a warning signal, it enters warning mode and only outputs manual assist torque. Error mode is used when the steering system detects an error signal and enters error mode, outputting zero power assist torque. The conversion relationships between the various working modes are as follows: The standby mode is entered after the steering system starts working, and the manual power steering mode is entered after the self-test is completed. If a warning signal is generated but no error signal is generated in standby mode, manual assist mode, automatic assist mode, superimposed torque mode, and intervention mode, then the system will enter warning mode. If an error signal is generated in standby mode, manual assist mode, automatic assist mode, superimposed torque mode, intervention mode, and warning mode, the system will enter error mode. In warning mode, if no warning signal or error signal is generated, it will enter standby mode. In error mode, if no warning signal or error signal is generated, it enters standby mode; If a warning signal is generated but no error signal is generated, then enter warning mode; In standby mode, if a signal from the vehicle requesting automatic power steering is received and the conditions for entering automatic power steering are met, then automatic power steering mode is entered; if a signal from the vehicle requesting superimposed torque mode is received, then superimposed torque mode is entered; if a signal from the vehicle requesting standby mode is received, then standby mode is entered. In automatic power steering mode, if a request for manual power steering is received from the vehicle, the system will enter manual power steering mode; if a request for torque boosting mode is received from the vehicle, the system will enter torque boosting mode; if a request for warning mode is received from the vehicle or the manual intervention conditions are met, the system will enter warning mode. In superimposed torque mode, if a request for manual power assist mode is received from the vehicle, the system will enter manual power assist mode; if a request for automatic power assist mode is received from the vehicle and the conditions for entering automatic power assist mode are met, the system will enter automatic power assist mode. In intervention mode, if a request for manual power assist is received from the vehicle, the manual power assist mode will be entered. Standby mode can be entered by the vehicle itself.

2. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The manual assist torque is obtained by subtracting the return-to-center control torque from the basic assist torque, subtracting the damping control torque, and adding the friction compensation torque and the inertia compensation torque.

3. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The automatic power assist mode must meet all of the following conditions and last for more than 0.5 seconds: vehicle speed less than or equal to the threshold of 60 km / h; hand torque less than or equal to the threshold of 1 Nm.

4. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The closed-loop control is specifically as follows: the control torque of item P is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by the P-item setting parameter; similarly, the control torque of item I is obtained by multiplying the difference between the target angular velocity and the actual angular velocity by the I-item setting parameter and then by the program running cycle. Both the P-item setting parameter and the I-item setting parameter are obtained by looking up a two-dimensional table based on the difference between the target angular velocity and the actual angular velocity. The two-dimensional table is calibrated using empirical values. The P-phase control torque and the I-phase control torque are added together to output the control motor action, which causes the steering wheel to reach the target angular velocity; Simultaneously, based on the difference between the target angle and the actual angle, when the difference between the target angle and the actual angle is greater than 50 degrees, the motor is controlled to move according to the target angular velocity; when the difference between the target angle and the actual angle is less than or equal to 50 degrees, the target angular velocity is obtained by looking up the data table based on the difference between the target angle and the actual angle to control the motor to move. The data table is set such that the smaller the difference between the actual angle and the target angle, the slower the target angular velocity, and the larger the difference, the faster the target angular velocity.

5. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The vehicle is at risk of deviating from its lane, including anti-tilt control, stability control, lane departure assist, crosswind compensation, or detection of driver fatigue.

6. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The conditions for manual intervention are: the absolute value of the manual torque signal exceeds 1 Nm and lasts for more than 0.5 s.

7. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The warning signal is triggered when any of the following conditions are met and last for more than 0.5 seconds: CAN message loss signal is triggered; external request target angle unavailable signal is triggered; VCU status abnormal signal is triggered; target angle absolute value is greater than 1224 degrees; target angular velocity signal absolute value is greater than 600 degrees / second; vehicle speed is greater than 150km / h; steering gear internal warning fault signal is triggered.

8. The power steering output of the commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The error signal indicates a failure to properly control the power steering, including steering sensor malfunction, chip malfunction, or motor malfunction.

9. The power steering output of a commercial vehicle electro-hydraulic power steering system according to claim 1, characterized in that, The assist torque, manual assist torque, and automatic output torque are all motor target torques after temperature compensation and torque limiting processing.

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