Design method of safety control system, safety control system and electric forklift

Abstract

The invention discloses a design method of a safety control system, the safety control system and an electric forklift, and belongs to the technical field of safety control systems of electric forklifts, and the safety control system comprises all main systems, subsystems, safety components and safety logic involved from safety input to safety output generation; a sensor, a switch, a power supply, a controller, an operating handle, a motor encoder and an accelerator pedal involved in the safety control system need to meet the average danger failure frequency when the specified safety function is met, the PLr level needing to be met is higher than the PLr level needed by the system, and related safety logic is subjected to program development through a V-model design method; when the safety control system breaks down, the system enters a safe controllable mode, personal and property damage is avoided, and risk reduction to a certain degree is achieved. The safety control system has the advantage that the safety control system meeting the performance level required by the safety requirement can be conveniently designed.

Description

Technical Field

[0001] The present invention relates to the technical field of functional safety control systems for electric forklifts, and in particular to a design method for a safety control system, a safety control system and an electric forklift. Background Art

[0002] Forklifts are industrial vehicles that can mechanize operations such as loading, unloading, stacking, and moving of goods without the need for auxiliary labor from loaders and unloaders, thereby reducing labor usage, lowering labor intensity, and improving operating efficiency.

[0003] Electric forklifts are used in a variety of industries, but there is a risk of unexpected behavior in electric forklifts. A safety control system needs to be designed to meet the performance level required by safety requirements and to minimize the risk of damage to people and property due to component failure or failure, logical defects, etc. Summary of the invention

[0004] The present invention aims to solve the technical problems mentioned in the above background technology. In a first aspect, a design method of a safety control system is provided to facilitate the design of a safety control system having a performance level that meets the safety requirements.

[0005] The second aspect provides a safety control system, which is designed using the design method of the safety control system of the first aspect to reduce the risk of accidents caused by component failure or malfunction, logical defects, etc., so as to avoid damage to people and property.

[0006] The third aspect provides an electric forklift equipped with the safety control system provided by the second aspect.

[0007] Based on the above objectives, the technical solution provided in the first aspect of the present invention is: a design method for a safety control system, the safety control system includes all main systems, subsystems, safety components, and safety logic involved from safety input to safety output; The sensors, switches, power supplies, controllers, operating handles, motor encoders, and accelerator pedals involved in the safety control system must meet the average dangerous failure frequency when the specified safety functions are met, and the PLr level that needs to be met must be higher than the PLr level required by the system. The safety logic involved is developed using the V-model design method. When a safety control system fails, the system will enter a safe and controllable mode to avoid damage to people and property, thereby reducing risks to a certain extent.

[0008] Furthermore, the safety control system depends on the average frequency of dangerous failures when performing the specified safety functions within a given time period (1 hour).

[0009] Furthermore, the safety control system depends on the average frequency of dangerous failures (PFH) when performing the specified safety function within a given time period (1 hour). To be able to control it within the expected average failure frequency, all main systems, subsystems, safety components, and safety logic involved from the safety input to the generation of safety outputs need to meet the specified performance level, that is, the performance level of the safety function (PL, divided into 5 levels from low to high, a, b, c, d, e) is defined by the average frequency of dangerous failures of the safety function per hour and the mean time to danger (MTTFd).

[0010] Furthermore, the safety control system includes various actions, namely, forward and backward movement, lifting and lowering of the fork, forward and backward tilting of the mast, etc., which all need to meet the safety control system requirements.

[0011] Furthermore, the security logic is developed by the V-model design method, that is, after the requirements are clarified, the test is carried out according to the set minimum test unit, mainly targeting the program code to ensure that each unit module is compiled correctly, and the units that have passed the unit test are combined into a complete system to test the functional implementation of the combined modules, whether the module interface connection is successful, and whether the data transmission is correct.

[0012] Furthermore, the integration test cases of the safety control system are written according to the implementation methods such as module functions and interfaces in the outline design to check whether the interfaces between software units are correct.

[0013] A second aspect of the present invention provides a safety control system designed by the design method of the safety control system provided by the first aspect.

[0014] A third aspect of the present invention provides an electric forklift equipped with the safety control system provided by the first aspect.

[0015] The advantages of the present invention compared with the prior art are: a functional safety control system and a fault diagnosis decision system applied to electric forklifts are established, which solves the problems of safety function protection of electric forklifts in driving control status monitoring, operating position monitoring, accidents when starting on flat roads, and accidental behavior monitoring during vehicle driving, fault tracing after functional protection, and fault decision processing and repair.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is an electric forklift motion control system according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the subsystem and logic of the safety control system of an embodiment of the present invention; Figure 3 This is a diagram showing the relationship between PL level and PFH; Figure 4 It is the definition of the average danger interval time of each subsystem and component in the embodiment of the present invention; Figure 5 It is a diagram of the V-model program development process. DETAILED DESCRIPTION

[0018] The present invention is described in further detail below.

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0020] Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, the purpose of the safety control system of this embodiment is to put the system into a safe and controllable mode when a system failure occurs to avoid damage to people and property. The safety control system is the key to whether the safety protection devices of mechanical equipment such as interlocking devices, light curtains, pressure-sensitive protection devices, etc. can reliably perform their safety functions, and it is also the key to ensuring the failure safety and fault safety of mechanical equipment.

[0021] In order to comprehensively reduce the risk level of mechanical equipment, it is necessary to use safety protection devices or systems with one or more safety functions to achieve a certain degree of risk reduction. Functional safety relies on the correct operation of the system or equipment on the input, and it is part of the overall safety. When each specific safety function is achieved and the required performance level (PLr) of each safety function is met, the functional safety goal is achieved, that is, when any random failure, system failure or common cause failure will not cause the failure of the safety system, thereby causing personal injury or death, environmental damage, and equipment property loss. In other words, the safety function of the device or control system should be guaranteed to be correctly implemented regardless of whether it is under normal circumstances or when there is a fault. The following is the design method and ideas of the safety control system.

[0022] Safety control system ( Figure 2) includes all main systems, subsystems, safety components, and safety logic involved from the start of safety input to the generation of safety output. The safety control system depends on the average frequency of dangerous failures (PFH) when performing the specified safety function within a given time period (1 hour). To be able to control it within the expected average failure frequency, all main systems, subsystems, safety components, and safety logic involved from the start of safety input to the generation of safety output need to meet the specified performance level, that is, the performance level of the safety function (PL, divided into 5 levels from low to high, a, b, c, d, e) is defined by the average frequency of dangerous failures (PFH) of the safety function per hour, and PFH is determined by the mean time to danger (MTTFd: Figure 4 ) to calculate ( Figure 3 ), for example: the average dangerous interval time is 60 years, then the average dangerous failure frequency per hour is 1 / 60*365*24=1.9*E-6, that is, the PFH level is within the range of 3*10-6 to 10-6. According to the performance of the average dangerous interval time of each subsystem and component, the performance level that the main system, subsystem, safety component and safety logic can meet can be calculated. Taking the average dangerous interval time of 60 years as an example, the safety performance level that the component can meet is PLc. The performance level (PLr) required for a safety function is proposed by the customer or specified in relevant regulations or standards when exported.

[0023] For electric forklift control system ( Figure 1 ), each action, i.e. forward and backward, lifting and lowering of the fork, forward and backward tilting of the mast, etc., must meet the requirements of the safety control system, that is, the sensors, switches, power supplies, controllers, operating handles, motor encoders, and accelerator pedals involved must meet the average frequency of dangerous failures when the specified safety functions are met. If the entire system needs to meet the PLc level, then the components included in the system must at least meet the PLc level. The safety logic involved is determined by the V-model ( Figure 5 ) design method for program development, that is, after clarifying the requirements, testing is carried out according to the set minimum test unit, mainly for the program code, to ensure that each unit module is compiled correctly, and to combine the units that have passed the unit test into a complete system, to test the functional implementation of the combination between the modules, whether the module interface connection is successful, whether the data transmission is correct, etc.

[0024] Integration test cases can be written based on the implementation methods of module functions and interfaces in the outline design to check whether the interfaces between software units are correct.

[0025] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A design method for a safety control system, characterized in that: The safety control system includes all main systems, subsystems, safety components, and safety logic involved from safety input to safety output; The sensors, switches, power supplies, controllers, operating handles, motor encoders, and accelerator pedals involved in the safety control system must meet the average dangerous failure frequency when the specified safety functions are met, and the PLr level that needs to be met must be higher than the PLr level required by the system. The safety logic involved is developed using the V-model design method. When a safety control system fails, the system will enter a safe and controllable mode to avoid damage to people and property, thereby reducing risks to a certain extent.

2. The design method of a safety control system according to claim 1, characterized in that: The safety control system depends on the average frequency of dangerous failures in performing the specified safety functions within a given time period (1 hour).

3. The design method of a safety control system according to claim 2, characterized in that: The safety control system depends on the average frequency of dangerous failures (PFH) when performing the specified safety function within a given time period (1 hour). To be able to control it within the expected average failure frequency, all main systems, subsystems, safety components, and safety logic involved from safety input to safety output must meet the specified performance level, that is, the performance level of the safety function (PL, divided into 5 levels from low to high, a, b, c, d, e) is defined by the average frequency of dangerous failures of the safety function per hour and the mean time to danger (MTTFd).

4. The design method of a safety control system according to claim 1, characterized in that: The safety control system includes that all actions, namely, forward and backward movement, lifting and lowering of the fork, forward and backward tilting of the mast, etc., need to meet the safety control system requirements.

5. The design method of a safety control system according to claim 1, characterized in that: The security logic is developed by the V-model design method, that is, after the requirements are clarified, the test is carried out according to the set minimum test unit, mainly targeting the program code to ensure that each unit module is compiled correctly, and the units that have passed the unit test are combined into a complete system to test the functional implementation of the combination between the modules, whether the module interface connection is successful, whether the data transmission is correct, etc.

6. The design method of a safety control system according to claim 1, characterized in that: The integration test cases of the safety control system are written according to the implementation methods of module functions and interfaces in the outline design to check whether the interfaces between software units are correct.

7. A safety control system, characterized in that: The design is performed by the design method of the safety control system described in any one of claims 1 to 6.

8. An electric forklift, characterized in that: Equipped with the safety control system described in claim 7.

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