Patent Publication Number: US-10761493-B2

Title: Safety module for an automation system, automation system and method for operating a safety module in an automation system

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a safety module for an automation system, the module comprising a communication interface designed for a signal-transmitting connection to a communication system, an output interface designed for a signal-transmitting connection to at least one user which can be fitted downstream and a processing device connected to the communication interface and the output interface and designed to process communication signals from the communication interface and to provide output signals to the output interface. The invention further relates to an automation system for operating at least one actuator and to a method for operating a safety module in an automation system. 
     The applicant distributes a safety module with the name of CPX-FVDA-P, which is designed for a communication with a higher-order safety-oriented control unit and which facilitates a safety-oriented influencing of users which can be fitted downstream. In this, we have to start from the fact that within current safety standards there is a need for a knowledge of the safety module concerning the users which can be fitted downstream, wherein relevant data of these users are, for example, directly input into the safety module with a suitable input device. 
     SUMMARY OF THE INVENTION 
     The invention is based on the problem of providing a safety module, an automation system and a method for operating a safety module in an automation system, wherein a simplified configuration of the safety module is ensured. 
     For a safety module of the type referred to above, this problem is solved by a safety module for an automation system, the module comprising a communication interface designed for a signal-transmitting connection to a communication system, an output interface designed for a signal-transmitting connection to at least one user which can be fitted downstream and a processing device connected to the communication interface and the output interface and designed to process communication signals from the communication interface and to provide output signals to the output interface, wherein it is provided that the processing device is designed for a detection of an actual component behaviour, using a control command contained in a communication signal and a component measured value contained in a communication signal, and for a comparison of a presettable component behaviour to the actual component behaviour as well as for a provision of a safety-oriented output signal to the output interface at a presettable divergence between the presettable component behaviour and the actual component behaviour. 
     The safety module is designed for placement between components of a lower-order control unit, which is, for example, designed for the control of a sub-function region of a complex machine. It may, for example, be provided that such a lower-order control unit is used for controlling a work manipulator in a machining cell, e.g. of a milling machine. The lower-order control unit, for example, comprises a bus node for communication with a higher-order control unit, which may in particular be designed as a programmable logic controller (PLC) and can be used for the control of several sub-function regions of the complex machine. The lower-order control unit further comprises a safety module connected to the bus node via an internal communication system, e.g. a proprietary bus system, for processing control signals of the higher-order control unit. In addition, the lower-order control unit comprises a plurality of functional modules, of which at least one is designed as an input module or as a combined input/output module and of which at least one further is designed as an actuator controller, e.g. as a solenoid valve for influencing a fluid flow for a fluid user. 
     The actuator controller is preferably designed as a safety-oriented functional module with characteristics in accordance with a presettable safety level. A safety-oriented functional module designed for blocking or enabling a fluid flow as a function of an output signal of the safety module will, for example, comprise an interconnection of several solenoid valves. Both in electric and in pneumatic terms, these solenoid valves are designed such that, for example at the non-appearance of the presettable electric output signal, a reliable blocking of a fluidic connection between a fluid source and an actuator connected to the safety-oriented functional module is ensured in order to move the actuator into a safe state by energy discharge. 
     The safety module is provided for the targeted activation of at least one, in particular safety-oriented, functional module and has to meet the requirements of the sought-for safety level within the preset safety category. A further aim is a largely independent function for the safety module. A particular aim is to limit a communication of the safety module with a safety control unit, which is a part of the higher-order control unit in particular, to a minimum. For this purpose, it is provided that the safety module independently makes decisions for a safety-oriented operation of at least one functional module of the lower-order control unit, which comprises the safety module and the at least one, in particular safety-oriented, functional module, without requiring any communication with the safety control unit, in particular by means of the higher-order control unit. 
     In order to achieve this independence of the safety module without having to perform a complex user-side configuration, it is provided that the safety module is configured with the aid of a configuration system of the higher-order control unit, which is also described as an engineering system. In the configuration process, at least one link of the safety module to at least one sensor assigned to an actuator to be controlled by the safety module is defined. In the lower-order control unit it is, for example, provided that sensor signals of a sensor are coupled in at an input module or a combined input/output module and there made available to the bus node via the internal communication system. The bus node is in turn designed to transfer incoming sensor signals to the safety module as component measured values within communication signals for use in a comparison to a presettable component behaviour. Here it is provided that the safety module is made aware by the configuration relayed by the higher-order control unit, in particular during a starting phase of the automation system, by means of at least one of the parameters contained in the configuration, from which input of the input module or the combined input/output module a component measured value is to be expected. A transmission of the configuration and the at least one parameter contained therein from the higher-order control unit via the bus system to the safety module does not have to meet any special safety targets, because it can be assumed that in the case of a faulty transmission the safety module will not undertake a correct assignment between incoming component measured values and the preset component behaviour. Accordingly, any malfunction will be uncovered even at a first provision of an output signal to the associated actuator controller, in particular at a validation of the function of the lower-order control unit at the commissioning of the automation system, which is not yet subject to normal operating conditions. 
     If an actuator controller connected to the safety module is activated by a control signal converted into an output signal by the safety module, the safety module is, owing to the parameterisation performed in the starting phase, configured to expect a component measured value which reflects a correct reaction of the actuator supplied with energy by the actuator controller. If this component measured value, which may for example be a sensor signal representing the arrival of the actuator at a presettable end position, arrives within a preset period of time, in particular within 60 seconds, after the provision of the respective output signal, the safety module can be configured to classify this component behaviour as regular and remains in a normal operating mode in which further incoming control signals are converted into output signals for the activation of the at least one connected actuator controller. If the component measured value does not correspond to the expected component behaviour within the preset period of time, however, for example because no sensor signal representing an expected arrival of the actuator at its end position arrives within the preset period of time, the safety module is configured to activate the actuator controller in such a way that the connected actuator is de-energised. This can, for example, be obtained by providing that a control voltage provided as an output signal of the actuator controller designed as a solenoid valve is switched off by the safety module, so that the actuator controller in turn interrupts a fluid flow to the actuator, which therefore does not move any further. Different procedures for ensuring a safe state for the actuator can be provided as well. 
     Advantageous further developments of the invention are the subject matter of the dependent claims. 
     It is expedient if the processing device is designed for a provision of an in particular safety-oriented communication signal to the communication interface in the presence of a presettable divergence between the presettable component behaviour and the actual component behaviour. The safety-oriented communication signal can inform the safety control unit that there has been a deviation from a normal operating state in the lower-order control unit, enabling the safety control unit to initiate further measures in order to set a safe state for the lower-order control unit affected or, if necessary, for all connected lower-order control units. 
     In an advantageous further development of the invention, it is provided that the processing device is designed for assigning the control command contained in the communication signal to the component measured value contained in the communication signal, using a parameter from a communication signal. This assignment establishes an unambiguous relationship between the component measured values received during the operation of the safety module and the control command which results in the intended action of the actuator if the safety module has been parameterised properly and if a functional chain comprising the safety module, the actuator controller activated thereby and the actuator assigned to the actuator controller functions properly. As soon as there is a malfunction in this functional chain, the safety module can detect a divergence between the actuator action intended by the control command and an actual actuator action and can then initiate the provided safety-oriented action by providing a suitable output signal. 
     According to a second aspect, the problem of the invention is solved by an automation system for operating at least one actuator. The automation system comprises a higher-order control unit to which are assigned a communication system and a safety control unit, as well as a lower-order control unit which is connected to the communication system and comprises a bus node, at least one input module, at least one safety module, in particular a safety module according to the invention, for the provision of operating energy to an actuator, at least one actuator connected to the safety module and at least one sensor device connected to the input module and designed for the detection of an actuator movement, wherein the bus node is designed for a conversion of communication signals of the higher-order control unit and of internal communication signals of the safety module and for a reception of component measured values from the sensor device connected to the input module and for transferring the component measured values to the safety module as a communication signal. 
     According to a third aspect, the problem of the invention is solved by a method for operating a safety module in an automation system. The method comprises the steps of: the provision of a communication signal from a higher-order control unit to a bus node, wherein the communication signal comprises at least one parameter describing a link between an input of an input module and an actuator, the reading-out and storage of the at least one parameter in the bus node and the transferring of the parameter to a safety module assigned to the bus node and capable of providing output signals for activating the actuator, the processing of the parameter in a processing device of the safety module in order to establish a communication link between the input of an input module, the bus node, the safety module and the actuator connected to the safety module. 
     Within the commissioning of the automation system, there is therefore, by means of a parameterisation contained in the configuration for the safety module, created a link both in the bus node and in the safety module, which link determines a signal flow from at least one sensor via an associated input module or input/output module to the bus node and from there to the safety module. In the parameterisation process, the bus node receives the information which sensor signal received from an input module or input/output module is to be transferred to the safety module as communication signal. In the parameterisation process, the safety module further receives the information which link is required between a control signal arriving in the subsequent normal operation of the automation system and a component measured value provided as communication signal. This link describes a relationship between a sensor signal arriving at an input of an input module and an output signal which is to be output by the processing device as a function of an incoming control signal and which is intended to lead to the activation of the actuator controller coupled to the actuator, the movement of which results in the change of the sensor signal. This establishes a circular relationship between the control signal, the safety module, the actuator controller, the actuator, the sensor mounted on the actuator, the input module connected to the sensor, the bus node and the safety module. By way of example, this circular relationship results in the maintenance of the output signal only if the safety module can determine from the actual component behaviour represented by the sensor signal, taking into account the control signal, that the actual component behaviour corresponds to a preset component behaviour. The preset component behaviour is in particular permanently and unalterably stored in the safety module. 
     A modification of the method provides that an input signal arriving at the input of the input module is made available to the bus node, and that the input signal is made available by the bus node to the safety module as a communication signal. The input signal is the sensor signal of the sensor which is connected to the input module and which is in turn assigned to an actuator and has the task of detecting an action of the actuator, in particular an actuator movement or an arrival at a presettable actuator position, and of making this available as a sensor signal to the input module. 
     A further modification of the method provides that the higher-order control unit provides the bus node with at least one control command which is transferred by the bus node to the safety module as a communication signal and converted by the processing device of the safety module into an output signal for the activation of at least one actuator, wherein the processing device performs a determination of an actual component behaviour using the control command and a signal course of the input signal made available by the input module via the bus node, and a comparison between a presettable component behaviour and the actual component behaviour, and provides a safety-oriented output signal to the output interface if there is a divergence between the presettable component behaviour and the actual component behaviour. The safety-oriented output signal is a shut-down signal in particular, by means of which the at least one actuator controller assigned to the safety module can be influenced in such a way that the connected actuator can be transferred to a safe, in particular de-energised, state. In a particularly preferred variant, it is provided that the shut-down signal serving as safety-oriented output signal causes the disconnection of a supply energy for the connected actuator controller, and that the actuator controller is designed such that it blocks a provision of energy, for example of compressed air, to the actuator if there is no supply energy. 
     Another modification of the method provides that the processing device makes available a safety-oriented communication signal to the communication interface for transferring to the safety control unit. In this way, the safety control unit can be informed directly that there is a problem in the respective lower-order control unit, and it can then take further measures for further operating or switching off the entire automation system in a way that meets preset safety requirements. 
     A further modification of the method provides that the presettable component behaviour is determined by a safety time interval and that the actual component behaviour is determined using a time interval which is measured from the provision of the output signal by the processing device to the output interface for activating the safety-oriented actuator controller to the arrival of a presettable input signal at the processing device. The presettable component behaviour is preferably permanently programmed into the safety module and cannot be changed by an operator. In a particularly preferred embodiment, the presettable component behaviour is a safety time interval of 60 seconds. 
     A further modification of the method provides that the safety module makes available a diagnostic signal to the communication interface if there is a divergence between the actual component behaviour and a presettable component behaviour. This diagnostic signal can be output before a detection of a presettable divergence between the presettable component behaviour and the actual component behaviour and is only used for informing the higher-order control unit. By way of example, such a diagnostic signal is output after 20 seconds, in particular to prepare any reactive measures of the higher-order control unit, which have to be taken on the arrival of the safety-oriented communication signal from the safety module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An advantageous embodiment of the invention is shown in the drawing, of which: 
         FIG. 1  is a diagrammatic representation of an automation system for the safety-oriented activation of at least one safety component, and 
         FIG. 2  is a flow diagram for an operation of a safety module. 
     
    
    
     DETAILED DESCRIPTION 
     An automation system  1  shown diagrammatically in  FIG. 1  is used for operating several actuators  2 ,  3 , which are designed as pneumatic cylinders purely by way of example and the movements of which may pose dangers, particularly for an operator not shown in the drawing. For this reason, the automation system  1  is fitted with at least one safety-oriented component to be described in greater detail below for a safety-oriented operation. 
     Purely by way of example, it is assumed that the automation system  1  comprises a higher-order control unit  4 , which is designed as a programmable logic controller (PLC) for communication with and for influencing a plurality of bus subscribers, in particular a lower-order control unit  5  and components connected thereto and described in greater detail below. For the communication between the higher-order control unit  4  and the lower-order control unit  5 , an external bus system  6  is provided which is connected to the higher-order control unit  4  by a bus interface  7  and to the lower-order control unit  5  by a bus interface  8 . In addition to the lower-order control unit  5 , which is also described as a bus subscriber, the external bus system  6  furthermore supports a pushbutton  9  as a further bus subscriber, whereby an emergency stop of the actuators  2 ,  3  operated by the automation system  1  can be initiated with the interposition of the lower-order control unit  5 . 
     To ensure a safety-oriented shut-down of the actuators  2 ,  3 , e.g. on operation of the pushbutton  9 , the higher-order control unit  4  is assigned a safety control unit  10 , via which both a safety-oriented communication with the pushbutton  9  and a safety-oriented communication with the lower-order control unit  5  via the external bus system  6  and the interposed higher-order control unit  4  are ensured. The processes provided in the safety control unit  10 , the higher-order control unit  4  and the lower-order control unit  5  are described in greater detail below. 
     Purely by way of example, the lower-order control unit  5  is constructed in a modular fashion from a plurality of components which communicate with one another by means of an in particular proprietary internal communication system  14 , which for reasons of clarity is shown in only one of the components of the lower-order control unit  5 . For communicating by means of the internal communication system  14 , each of the components has a mutually assigned communication interface. For coupling the internal communication system  14  to the external bus system  6  provided by the higher-order control unit  4 , the lower-order control unit  5  comprises the bus node  12 , which is designed for a bidirectional conversion of signals between the external bus system  6  and the internal communication system  14  of the lower-order control unit  5 . 
     In the line-up direction  15 , which runs to the right purely by way of example according to  FIG. 1 , the bus node  12  is adjoined by an input module  17  with several inputs  18 , which are for example provided for connecting sensor lines  45 ,  46 ,  47  of sensors  19 ,  20 ,  21 . The input module  17  is designed for detecting and pre-processing sensor signals of the sensors  19  to  21 . The input module  17  is configured in such a way that pre-processed sensor signals of the sensors  19  to  21  are made available to the bus node  12  via the internal communication system  14 , from where they can, for example, be conveyed to the higher-order control unit  4 . 
     The input module  17  is adjoined by a safety module  22 , which comprises a communication interface  23 , an output interface  24 , a processing device  25  and a storage device  26 . Purely by way of example, the communication interface  23  is designed for a bidirectional communication with the bus node  12  via the communication system. The output interface  24  is designed for a provision of electric output signals to the downstream functional modules. 
     The processing device  25  is preferably designed as a microprocessor and provided for executing a presettable programme, in particular a software. In the production or configuration process of the safety module  22  in particular, this programme can be stored in the storage device  26  and from there read out by the processing device  25  for the operation of the safety module  22 . 
     Purely by way of example, the safety module  22  is adjoined by a plurality of functional modules designed as valves  27  and safety-oriented valves  28 . Each of the valves  27 ,  28  is designed for the provision of a fluid flow to an associated fluid user  2 ,  3  via fluid lines  40 ,  41 ,  42 . For reasons of clarity, only the safety-oriented valves  28  are connected to the associated fluid users, i.e. the actuators  2  and  3 . The valves  27 ,  28  are designed as solenoid or piezoelectric valves for example and are switched on or off by the safety module by providing electric energy in the form of output signals, or they are operated as proportional valves in freely selectable intermediate positions. 
     Purely by way of example, the safety-oriented valves  28  are in fluidic terms designed in accordance with the requirements of a safety category required for the automation system  1 . As an example, it is provided that each of the safety-oriented valves comprises an internal series circuit of two monostable solenoid valves not shown in the drawing, so that a fluid flow can be enabled by the respective safety-oriented valve  28  only if both internal solenoid valves simultaneously enable the associated fluid passage in the presence of a suitable output signal of the safety module  22 . The safety-oriented valves  28  can furthermore comprise further electric or electronic measures, for example to facilitate a detection for the switching state of the respective internal solenoid valve to provide a fault message to the safety module  22  if applicable. 
     It is for example provided that the safety module  22  receives a safety signal from the safety control unit  10  on the operation of the pushbutton  9 . This safety signal is fed into the internal communication system  14  of the lower-order control unit  5  via the higher-order control unit and the external bus system  6 . By means of this safety signal, an influencing, in particular a disconnection, of an energy flow, in particular a fluid flow, to the actuators  2  and  3  is to be effected, for example. 
     According to the flow diagram of  FIG. 2 , in step A the assignment of at least one sensor  19 ,  20 ,  21  to a respective input  18  of the input module  17  is initially input into an engineering system of the higher-order control unit  4 . This initially determines to which of the inputs  18  which of the sensors  19 ,  20 ,  21  are connected. Based on this information, the safety module  22  is in a following step made aware of which incoming communication signal stems from which of the actuators  2 ,  3  and the associated sensors  19 ,  20 ,  21 . This input is preferably carried out using a computer-based graphical user interface of the engineering system not shown in detail, by means of which the higher-order control unit  4  and the lower-order control unit  5  connected thereto can be defined, configured and parameterised. 
     The input parameters are then transferred to the higher-order control unit  4  in step B. 
     During a starting phase of the automation system  1 , the parameters are in step C transmitted from the higher-order control unit  4  to the bus node  12  in accordance with an external bus protocol such as PROFIBUS, in particular within a data transmission which is not especially secured. 
     In step D, it is provided that the bus node  12  reads the parameters out of the bus telegram transmitted via the external bus system and stores them for its own use and conveys them to the downstream safety module  22  for its use. The bus node  12  is configured for conveying input signals made available by the input module  17  to the safety module  22  and, if applicable, to the higher-order control unit  4 , using the stored parameters as communication signals. 
     The processing device  25  of the safety module is configured for assigning the connected valves  27 ,  28  to the inputs  18  of the input module  17  during the starting phase of the automation system  1 , using the parameters arriving in step E from the bus node  12 , so that, in a subsequent normal operation of the automation system  1 , the sensor signals made available by the bus node  12  as communication signals can be correctly related to the actuator controllers serving as valves  27 ,  28  and to the actions of the connected actuators  2 ,  3  as initiated by the actuator controllers  27 ,  28 . 
     According to step F, a control signal is made available by the higher-order control unit  4  to the safety module  22 . Here, the processing device  25  of the safety module  22  is configured for converting the control signal transmitted by the bus node as communication signal into an output signal which is made available to one of the valves  27 ,  28  at the output interface  24 . The valve  27 ,  28  activated by the output signal is configured for enabling a fluid flow to the respective actuator  2 ,  3 , so that it can initiate a movement of its piston rod  43 ,  44 . By way of example, it is provided that the control signal effects a ventilation of a first working chamber of the actuator  2  and a venting of a second working chamber of the actuator  2 , thereby moving the piston rod  43  of the actuator  2 . 
     If the actuator  2 ,  3  can perform the intended movement, a sensor signal of at least one sensor  19 ,  20 ,  21  assigned to the respective actuator  2 ,  3  changes. This sensor signal arrives at the input  18  of the input module  17  and is transferred by the input module  17  to the bus node  12  in step G. Given the stored parameterisation, the sensor signal is there transferred to the safety module  22  as communication signal. 
     It is furthermore provided that, on provision of the output signal aimed at changing the movement state to the output interface  24 , a chronometry is started in the safety module  22 , the current value of which is continuously compared to the presettable component behaviour, which is likewise available in the form of a time interval, as indicated by step H. If the processing device  25  can detect from the signal course of at least one of the sensors  19 ,  20 ,  21  that the movement state of the actuator  2 ,  3  has changed and this change of the movement state has occurred within the presettable component behaviour available in the form of a time interval, which is shown in step I 1 , the associated actuator controller  27 ,  28  continues to operate in accordance with the programme running in the safety module  22 , as indicated in step J 1 . By way of example, it is provided that the flow diagram is run through again from step F. 
     If the current chronometry value has exceeded the time interval according to the presettable component behaviour, a divergence between the preset component behaviour and the actual component behaviour is detected by the processing device  25  according to step I 2 , and consequently the provision of the output signal to the output interface  24  is blocked immediately and without any consultation with the higher-order control unit  4 . In this way, the actuator  2 ,  3  can, by way of the selected valve  27 ,  28 , be influenced in such a way that it adopts a safe, in particular de-energised, state as quickly as possible. If the sensor  19 ,  20 ,  21  detects a change of state in the associated actuator  2 ,  3  and this information is transferred via the communication path described above to the processing device  25  and the comparison to the control signal indicates that such a change of state does not correspond to the preset component behaviour, the safety module  22  can block the provision of the output signal to the output interface  24  immediately and without any consultation with the higher-order control unit  4 . 
     It can further be provided that the safety module  22  makes available a safety-oriented communication signal to the safety control unit  10  in accordance with step J 2 . This informs the latter that the activated actuator  2 ,  3  is brought into a safe state, so that the safety control unit  10  and, if applicable, the higher-order control unit  4  can take further measures, e.g. to make the automation system  1  available for maintenance as quickly as possible and/or to inform an operator about the action of the safety module  22 .