Drive-by-wire chassis heterogeneous actuator cooperative control method considering low computing power and high response

Abstract

The application relates to a drive-by-wire chassis heterogeneous actuator cooperative control method considering low computing power and high response. The method comprises the following steps: for a plurality of sub-function modules of a drive-by-wire chassis heterogeneous actuator, taking the actuation frequency of each module actuator as a control frequency, calculating the disturbance contribution amount between the modules, and asynchronously updating the control actions of each sub-function module; when the state of the sub-function module meets the triggering condition of a preset event, at least one target sub-function module is matched based on an instability event-sub-function module mapping relationship, and the control actions of all the target sub-function modules are updated through interconnection iteration. The application fully utilizes the unique advantages of modular control, designs an asynchronous triggering and event triggering control strategy, and after the combination of the two, the calculation burden is effectively reduced, the calculation efficiency of the modular control algorithm is improved under the premise of ensuring the control efficiency, the response delay to sudden disturbances is reduced, and the chassis stability under extreme operating conditions is ensured.

Description

Technical Field

[0001] This invention relates to the field of drive-by-wire chassis technology, and in particular to a collaborative control method for heterogeneous actuators in drive-by-wire chassis that balances low computing power and high response. Background Technology

[0002] Current drive-by-wire chassis systems mostly design controllers for each type of actuator as independent subsystems, neglecting coordination between subsystem modules and overall system optimization. On one hand, the independent design of each subsystem may lead to control conflicts, thus reducing resource utilization efficiency. On the other hand, without unified scheduling, each subsystem may update its state or perform actions at different times, significantly increasing system complexity and making it prone to local optima.

[0003] Meanwhile, the stability control system of the drive-by-wire chassis has different intervention frequencies in the longitudinal, lateral, and vertical directions. If a centralized optimization is used to coordinate the heterogeneous actuator system and synchronously calculate the control quantities of all actuators at a fixed time period, it will be necessary to select the operating frequency of high-frequency actuators as the overall control scheduling frequency of the system. However, the physical characteristics of various types of actuators, such as drive, braking, steering, and suspension actuators, determine that their responsive operating frequencies are not the same. Some modules with slower operating frequencies still need to participate in the calculation at a high frequency, resulting in the actual calculation results not being fully applied to the chassis motion control system and failing to make full use of limited onboard computing resources. The chassis stability control algorithm triggered at a fixed time period is also prone to problems such as untimely response when facing extreme and sudden events. In order to fully leverage the advantages of multi-actuator collaboration in the drive-by-wire chassis system, it is necessary to design an efficient asynchronous collaboration strategy to reduce computing power requirements and improve real-time response capabilities. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a collaborative control method for heterogeneous actuators of a drive-by-wire chassis that balances low computing power and high response, so as to achieve the goal of improving computing efficiency while ensuring real-time performance.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One aspect of the present invention provides a method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, comprising the following steps:

[0007] For the pre-defined multiple sub-functional modules of the heterogeneous actuator in the drive-by-wire chassis, the disturbance contribution between sub-functional modules is calculated. The actuation frequency of each sub-functional module's actuator is used as the corresponding control frequency. The control actions of each sub-functional module are asynchronously updated based on the calculated disturbance contribution. When the state of a sub-functional module meets the triggering conditions of a preset event, at least one corresponding target sub-functional module is matched based on the instability event-sub-functional module mapping relationship. Through interconnection and iteration, all target sub-functional modules simultaneously update their control actions. As a preferred technical solution, the sub-functional modules are modeled as follows:

[0008]

[0009] x i (k+1)=A ik,t x i (k)+B ik,t u i (k)+∑W ij (k)

[0010] Among them, X i U is the state variable of the actuator corresponding to sub-functional module i. i A is the control input for the actuator. i and B i It is the state transition matrix, W j A is the contribution of other sub-functional modules to the disturbance of the overall state. ik,t =I+ΔT i A i B ik,t =ΔT i B i I is the identity matrix, ΔT i W represents the discrete step size of the controller of the i-th sub-functional module. ij It is the disturbance contribution of sub-functional module j to sub-functional module i.

[0011] As a preferred technical solution, based on patent application "2023109395104, A Modular Control Method for a Drive-by-Wire Chassis Considering Actuator Characteristics", a sub-functional module control model considering the differentiated dynamic characteristic responses of actuators is constructed, and the integration of different sub-functional modules is achieved through distributed control. The calculation of the disturbance contribution includes the following steps:

[0012] For sub-functional modules other than sub-functional module i, the prediction sequence is supplemented with the last prediction value of the sub-functional module as a reference, so that the sequence length of the other sub-functional modules is greater than or equal to the sequence length of sub-functional module i.

[0013] The projection of the state of sub-functional module i onto the prediction sequences of other sub-functional modules at the current prediction time is taken as the perturbation contribution.

[0014] As a preferred technical solution, the asynchronous updating of the control actions of the sub-functional modules, using the actuation frequency of each sub-functional module's actuator as the corresponding control frequency for the module, specifically includes:

[0015] Each sub-functional module updates its control actions according to its own operating frequency, and only one sub-functional module is updating at any given time. When multiple sub-functional modules need to be updated at the same time, they are updated in order of increasing operating frequency.

[0016] As a preferred technical solution, the process of simultaneously updating the control actions of all target sub-functional modules through interconnected iteration includes the following steps:

[0017] Initialize the control actions of each target sub-functional module to the control actions of the previous moment;

[0018] For any target sub-functional module, calculate the disturbance contribution based on the control actions of other target sub-functional modules, update the control output of the current target sub-functional module, calculate the corresponding control output for all target sub-functional modules in turn, obtain the control output set, and repeat this step multiple times until the stopping condition is met.

[0019] Each target sub-function module is updated synchronously based on the current set of control outputs.

[0020] As a preferred technical solution, the stopping condition is state convergence and / or the computation time reaching a threshold.

[0021] As a preferred technical solution, the construction of the instability event-sub-functional module mapping relationship includes the following steps:

[0022] The status data of each sub-functional module is collected, the triggering state of the instability event is obtained by principal component analysis, and the mapping relationship between the instability event and the sub-functional module is obtained based on the fault tree. The triggering condition of the instability event is that the status characteristic value of the drive-by-wire chassis system or the sub-functional module exceeds a set threshold.

[0023] As a preferred technical solution, after all target sub-functional modules update their control actions simultaneously through interconnected iterations, the control method of asynchronously updating the sub-functional modules is returned.

[0024] In another aspect, an electronic device is provided, comprising: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the above-described method for coordinated control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response.

[0025] In another aspect, the present invention provides a computer-readable storage medium including one or more programs executable by one or more processors of an electronic device, the one or more programs including instructions for performing the above-described method for coordinated control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) Improving computational efficiency while ensuring real-time performance: Under normal circumstances, this invention asynchronously updates the control actions of each sub-functional module using the actuator actuation frequency of each sub-functional module as the corresponding control frequency. Because of this asynchronous update, each sub-functional module can operate at its own optimal actuation frequency without needing a uniform frequency, thus fully utilizing the performance of each sub-functional module. Furthermore, to ensure stability, when the state of a functional module meets the triggering conditions of a preset event, interconnected iterations cause all target sub-functional modules to update their control actions simultaneously. This allows for timely responses when system adjustments are needed, ensuring stability. This combination saves computational resources while maintaining system real-time performance.

[0028] (2) Improved control flexibility and stability: Event-triggered control only performs control actions when the system state changes significantly. Therefore, when the system is relatively stable, the control frequency can be reduced, thereby avoiding unnecessary control overhead. Asynchronous trigger control provides a stable reference control frequency, so that the system is always in a stable state.

[0029] (3) Improved algorithm adaptability and robustness: Since the event triggering rules and asynchronous triggering control parameters can be adjusted according to specific circumstances, the combination of asynchronous triggering and event triggering control can better adapt to the control requirements of different systems and working conditions. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response.

[0031] Figure 2 A diagram illustrating the exchange of contributions between submodules;

[0032] Figure 3 This is a schematic diagram of a control law that combines asynchronous triggering and event triggering. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0034] Example 1

[0035] See Figure 1 In view of the shortcomings of the aforementioned existing technologies, this embodiment provides a collaborative control method for heterogeneous actuators of a drive-by-wire chassis that balances low computing power and high response, aiming to improve the working efficiency of modular systems for drive-by-wire chassis and the stability of the control system under extreme working conditions.

[0036] This method includes the following steps:

[0037] S1 is designed as an independent controller for the sub-functional modules of different actuators in the drive-by-wire chassis. Based on the actuator actuation frequency, an optimized scheduling frequency that takes into account both the actuator response characteristics and control effect is selected. The optimal control law that meets the characteristics of each sub-functional module and can respond to control requests in a timely manner is designed. The efficient integration and control coordination of the heterogeneous actuators of the chassis are realized through an asynchronous triggering mechanism.

[0038] Step S1 specifically includes the following steps:

[0039] S11 is designed as an independent controller for the sub-functional modules of different actuators of the wire-controlled chassis.

[0040] S12, Select an optimized scheduling frequency that takes into account both the actuator response characteristics and control effect based on the actuator actuation frequency, and design the optimal control law that meets the characteristics of each sub-functional module and can respond to control requests in a timely manner.

[0041] S13 achieves efficient integration and coordinated control of heterogeneous actuators in the chassis through an asynchronous triggering mechanism.

[0042] In step S11, the state equation of the submodule is:

[0043]

[0044] X i For the state variables of the corresponding actuator, U i A is the control input for the corresponding actuator. i and B i W is the corresponding state transition matrix. j It represents the contribution of other modules to the disturbance of the overall state.

[0045] Asynchronous triggering control laws need to be implemented in conjunction with distributed model predictive control; therefore, the state equations of the submodules need to be transformed into discrete forms.

[0046] x i (k+1)=A ik,t x i (k)+B ik,t u i (k)+∑W ij (k) (2)

[0047] Where A ik,t =I+ΔT i A i B ik,t =ΔT i B i I is the identity matrix, ΔT i W represents the discrete step size of the i-th submodule controller. ij It represents the perturbation contribution of module j to module i.

[0048] Traditional control methods often select the operating frequency of high-frequency actuators as the overall control and scheduling frequency of the system. However, the operating frequency of the actuators corresponding to each sub-functional module is not the same. This results in some modules with slow operating frequencies still needing to participate in calculations at high frequencies, and the actual calculation results are not fully applied to the actuators, wasting a lot of computing resources.

[0049] In step S12, to obtain the optimal control law that balances computational efficiency improvement and control effect, this step discloses how to select the control frequencies of different sub-modules, and how the contribution sequences between sub-modules are updated and interacted, specifically as follows:

[0050] From the perspective of reducing wasted computing resources, it is necessary to ensure that the control actions after each computational update have a chance to be executed. That is, for a sub-functional module i, its control frequency f i,c and the corresponding actuator's operating frequency f i,a Condition f should be satisfied i,c ≤f i,a From the perspective of ensuring algorithm performance, control actions need to be updated as frequently as possible to adapt to rapid changes in the system state. Therefore, the actuator's actuation frequency is chosen as the control frequency of this module, i.e., f. i,c =f i,a Accordingly, the distance between the controller and the walk distance is Δτ. i =1 / f i,c .

[0051] Since different actuators may have different characteristics, the discrete step size Δτ of the i-th module controller is... i The distance between the j-th module controller and the distance Δτj They are not necessarily the same.

[0052] When using distributed model predictive control, the discrete step size ΔT of the controllers of different sub-modules in formula (2) is... i No, they are not the same. Therefore, information interaction between modules will experience spatiotemporal misalignment, requiring an understanding of the contribution interaction sequence w between modules. ij Additional processing is required.

[0053] like Figure 2 The present invention provides a method for updating contribution sequences:

[0054] Step 1, calculate the contribution sequence W ij At that time, for the prediction sequence obtained from the previous calculation of module j If the final prediction time t of module i i +N p ΔT i The module j was greater than the predicted endpoint t in the previous calculation. j +N p ΔT j The last predicted value of module j For reference, the original predicted sequence W j,t Supplementation is performed. The supplementary predicted sequence is obtained. Until the time scale requirement of module i can be met, i.e., t j +(N p +n)ΔT j The predicted end time t of module i is greater than i +N p ΔT i , where n∈N + This represents the additional sequence length that needs to be added.

[0055] Step 2, calculate the contribution sequence W ij At that time, the current prediction time t of module i will be... i +mΔT i The state projection onto the prediction sequence of module j is taken as the contribution value of module j to module i at that moment, thus obtaining the contribution sequence of module j to module i.

[0056] Step 3, when calculating the total contribution of other modules to module i, use the prediction time t of module i as the reference. i +mΔT i Alignment yields the total perturbation contribution sequence. Where m∈{1,2...N} p}

[0057] Step S13 is as follows:

[0058] S131, each module triggers calculations according to its own scheduling cycle. When the predetermined trigger time is reached, only one module can execute the calculation. If multiple modules simultaneously meet the predetermined trigger conditions at a certain moment, the module with the longest trigger time interval is calculated first, and the other modules are triggered in turn.

[0059] S132, During the calculation process, the cached sequences determined by other modules are stored in real time as contribution sequences received from that module and incorporated into the prediction model;

[0060] S133 obtains an approximate Pareto optimal control effect through alternating calculations, achieving optimal overall system performance while ensuring the performance of each module.

[0061] S2 monitors changes in the state of the drive-by-wire chassis system and modules, establishing a correspondence between the chassis system state and the corresponding sub-functional modules. When the system or module state characteristic value exceeds a set threshold, an instability event is considered triggered. An event-triggered control law enables adaptive iterative update control of the corresponding sub-functional modules, ensuring the overall stability of the system and modules.

[0062] Step S2 specifically includes the following steps:

[0063] S21 involves monitoring the system and module states, designing appropriate state combinations as different event triggering conditions, analyzing the impact of specific modules on the system state, and establishing a mapping relationship between system states and module impacts. S21 specifically includes the following steps:

[0064] S211, filter the system and module states and select appropriate states as candidate event trigger states;

[0065] S212, starting from the candidate event trigger state, finds all possible direct causes of events at each level step by step until the analysis reaches each sub-functional module.

[0066] The selection of candidate event trigger states can be achieved using principal component analysis to reduce state complexity and obtain the main trigger states. From the candidate states to each level of sub-functional modules, fault tree theory can be used to find the influence mapping relationship between the overall vehicle state and the various actuators of the chassis.

[0067] S22, when the trigger event condition corresponding to a sub-functional module is not met, the control action of that module is not updated; after the trigger event condition corresponding to that module is met, a new control law is designed to re-coordinate the control actions of that module with other modules to ensure the stability of the entire system. Step S22 is as follows:

[0068] When the system state triggers the corresponding threshold, the sub-functional module affecting that state is identified. Regardless of how much time has passed since the last calculation, the corresponding sub-functional module must simultaneously execute a synchronization step to update its control actions, while the control actions of the remaining modules remain unchanged.

[0069] In event-triggered states, the system state needs to be updated rapidly. When multiple modules are triggered simultaneously, the method of sequentially triggering high-frequency and low-frequency modules is insufficient to meet the system's control precision requirements. Therefore, an interconnected iterative approach is adopted to perform synchronization steps, updating the control actions of the corresponding modules to achieve event-triggered control.

[0070] Step 1: When a certain event is triggered, initialize the control actions of all modules to the control actions of the previous moment, i.e., U. i,t ={u i,t_last}

[0071] Step 2, for one of the triggering modules k, according to the module's control action set U i,t Calculate the total disturbance contribution of all other modules to module k, ∑w kj，i .

[0072] Step 3: Solve to obtain the control output u of module k. k,t Update the control action set U i,t .

[0073] Step 4: Repeat steps 2-3 to iteratively solve for the control outputs of all triggering modules and update the control action set U. i,t .

[0074] Step 5: When the state converges or the computation time reaches the upper limit, stop the iterative solution and output the final updated control actions of each triggering module.

[0075] Each module performs repeated iterations of calculations until "the state converges or the calculation time reaches its limit," and then simultaneously outputs updated control actions.

[0076] S3 combines asynchronous triggering and event triggering strategies to design a dynamic triggering control law that integrates asynchronous triggering based on actuator response characteristics and vehicle stability state event triggering. This improves the response speed of the chassis motion control system and the stability of the vehicle under extreme conditions while ensuring computational efficiency.

[0077] Under asynchronous triggering control laws, the triggering frequency of sub-functional modules can be adjusted by utilizing the actuator's operating frequency to save computational resources. However, when the chassis system is unstable, the fixed-time triggering method, which updates the control state only through a single sub-functional module, can still cause the overall chassis system to exceed stability control limits under extreme operating conditions. Therefore, this invention combines event-triggered control with a dynamic triggering control law. Figure 3 As shown, step S3 specifically includes the following steps:

[0078] S31, when the system state is stable, an asynchronous triggering control law is adopted, and each sub-module performs calculations according to its own actuator operating frequency.

[0079] S32 monitors the chassis domain system status and is designed to trigger events. When an event is triggered, the corresponding actuator performs interconnected iterative calculations at a uniform, fixed frequency until the system status returns to normal.

[0080] S33, when the system returns to normal, restore the original asynchronous trigger control law.

[0081] In a specific embodiment, the following steps are included:

[0082] Step 1: In order to achieve vehicle drive-by-wire chassis handling stability control, the whole vehicle model is divided into three sub-functional modules—front wheel steering assist, rear wheel steering assist, and torque vector control—for independent modeling and control, based on the function of the actuators.

[0083] Step 2: Determine the scheduling frequency of the three sub-functional modules based on the operating frequencies of the front wheel steering motor, rear wheel steering motor, and drive / brake motor.

[0084] Step 3: Based on the characteristics of each sub-functional module, design asynchronous triggering coordination control laws with different scheduling frequencies.

[0085] Step 4: Monitor the status of the system and modules, establish a mapping relationship between abnormal events and actuator actions, and design event-triggered control laws.

[0086] Step 5: Based on asynchronous triggering, integrate event triggering to design a hybrid mode coordination control law.

[0087] Example 2

[0088] This embodiment provides an electronic device, including: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the wire-controlled chassis heterogeneous actuator cooperative control method as described in Embodiment 1, which balances low computing power and high response.

[0089] Example 3

[0090] This embodiment provides a computer-readable storage medium including one or more programs executable by one or more processors of an electronic device, the one or more programs including instructions for executing the wire-controlled chassis heterogeneous actuator cooperative control method as described in Embodiment 1, which balances low computing power and high response.

[0091] Compared with existing technologies, this invention fully utilizes the unique advantages of modular control by designing asynchronous triggering control strategies and event-triggered control strategies. The combination of these two strategies effectively reduces the computational burden, enabling the modular control algorithm to achieve rapid response while ensuring control performance. This results in improved system computational efficiency and stability under extreme conditions.

[0092] The present invention has the following advantages:

[0093] First, it improves the real-time performance of the algorithm and saves computational resources: By using event-triggered control when some critical states change, the system can respond promptly when adjustments are needed, while asynchronous triggering control ensures a certain control frequency when necessary. This combination saves computational resources while maintaining system real-time performance.

[0094] Second, it improves control flexibility and stability: Event-triggered control only initiates control actions when the system state changes significantly, thus reducing the control frequency when the system is relatively stable and avoiding unnecessary control overhead. Asynchronous triggering control, on the other hand, provides a stable reference control frequency, ensuring that the system remains in a stable state.

[0095] Third, the algorithm's adaptability and robustness are improved: Since the event triggering rules and asynchronous triggering control parameters can be adjusted according to specific circumstances, the combination of asynchronous triggering and event triggering control can better adapt to the control requirements of different systems and working conditions.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, characterized in that, Includes the following steps: For the multi-sub-functional modules of the heterogeneous actuator of the drive-by-wire chassis, the disturbance contribution between the sub-functional modules is calculated, and the actuation frequency of each sub-functional module actuator is used as the corresponding control frequency of the module to asynchronously update the control action of each sub-functional module. When the state of a sub-functional module meets the triggering conditions of a preset event, based on the instability event-sub-functional module mapping relationship, at least one corresponding target sub-functional module is matched, and through interconnection iteration, all target sub-functional modules simultaneously update their control actions. The sub-functional modules are modeled as follows: in, Sub-functional modules The state variables of the corresponding actuator, For the control input of the actuator, and It is the state transition matrix. It represents the contribution of other sub-functional modules to the disturbance of the overall state. , , It is a unit array. Representing the i The distance between the controller of each sub-functional module is long. It is a sub-functional module j Pair Functional Module i The disturbance contribution is calculated by the following steps: For the sub-division function module i For other sub-modules besides the one mentioned above, the prediction sequence is supplemented with the last prediction value of the sub-module as a reference, so that the sequence length of the other sub-modules is greater than or equal to that of the sub-module. i The sequence length; Sub-functional modules i The state projection onto the prediction sequences of other sub-functional modules at the current prediction time is used as the perturbation contribution. The method of asynchronously updating the control actions of sub-functional modules by using the actuation frequency of each sub-functional module's actuator as the corresponding control frequency of the module specifically includes: Each sub-functional module updates its control actions according to its own operating frequency, and only one sub-functional module is updating at any given time. When multiple sub-functional modules need to be updated at the same time, they are updated in order of increasing operating frequency.

2. The method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, as described in claim 1, is characterized in that... The process of simultaneously updating the control actions of all target sub-functional modules through interconnected iteration includes the following steps: Initialize the control actions of each target sub-functional module to the control actions of the previous moment; For any target sub-functional module, calculate the disturbance contribution based on the control actions of other target sub-functional modules, update the control output of the current target sub-functional module, calculate the corresponding control output for all target sub-functional modules in turn, obtain the control output set, and repeat this step multiple times until the stopping condition is met. Each target sub-function module is updated synchronously based on the current set of control outputs.

3. The method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, as described in claim 2, is characterized in that... The stopping condition is state convergence and / or the computation time reaching a threshold.

4. The method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, as described in claim 1, is characterized in that... The construction of the instability event-sub-functional module mapping relationship includes the following steps: The status data of each sub-functional module is collected, the triggering state of the instability event is obtained by principal component analysis, and the mapping relationship between the instability event and the sub-functional module is obtained based on the fault tree. The triggering condition of the instability event is that the status characteristic value of the drive-by-wire chassis system or the sub-functional module exceeds a set threshold.

5. The method for collaborative control of heterogeneous actuators in a drive-by-wire chassis that balances low computing power and high response, as described in claim 1, is characterized in that... After all target sub-functional modules update their control actions simultaneously through interconnected iterations, the control method of asynchronously updating sub-functional modules is returned.

6. An electronic device, characterized in that, include: One or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the wire-controlled chassis heterogeneous actuator cooperative control method as described in any one of claims 1-5, which combines low computing power and high response.

7. A computer-readable storage medium, characterized in that, It includes one or more programs that can be executed by one or more processors of an electronic device, the one or more programs including instructions for executing the wire-controlled chassis heterogeneous actuator cooperative control method as described in any one of claims 1-5, which combines low computing power and high response.

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