MONITORING USAGE OF A POWER TOOL

Technical field

The present invention relates generally to a method, a monitoring node and a computer program of monitoring usage of a power tool.

Background art

Power tools and systems with power tools, including portable power tools such as power wrenches operated by an operator, are often used in production work. A common application is in assembly lines. Nowadays, power tools in assembly lines may have a controller connected to them and the controller controls the work performed by the tool so that the tool works automatically. With other words the controller sees to that the tool is operated correctly, e.g. performing a wrench operation with the correct torque etc. Sometimes it is necessary to update the controller with new information. For example, the tools may have to perform new operations, change dimensions or torque or just adjust the current operation for a better performance.

In PCT/EP2015/064814 there is disclosed a tool communications network for enabling remote control of power tools. This tool communications network is very useful for performing updates to many tool controllers at the same time, minimizing the time of an operator during the update. The mentioned tool communication network may also be used by the tool controllers to collect data of the result of work performed by the power tools, such as collecting the torque used for tightening a bolt or nut. Collecting such data is valuable for increasing traceability of products produced in an assembly line. Thus, the tool communication network has greatly improved the efficiency and quality of work at assembly lines.

However, there are still improvements to be done. One such improvement area is to foresee or detect impending tool failure and what the cause for tool failure is. Today, a production technician may through experience know what station in the assembly line that usually has problems with tool usage or with operator behavior. This experience may be gained by observing the operators. Observing operator behavior to gain an overview of the assembly line requires a lot of experience and also time from the production technician. Since the production technician only can be at one place at a time it will not only be difficult, but impossible, to observe the whole assembly line at once. This will lead to disturbances in the production, since there will be failures do to defective power tools or wrong operator behavior.

Thus, there is a need to get a better overview of an assembly line in order to foresee and reduce failures that may lead to interrupted production. Summary

It is an object of the present invention to address at least some of the problems and issues outlined above. It is possible to achieve these objects and others by using a method, a monitoring node and a computer program for monitoring usage of a power tool. According to one aspect, a method is performed by a monitoring node that is associated with a tool communication network to which also the power tool is connected. The method comprises receiving, from the power tool, parameter values relating to an acceleration force of the power tool, retrieving a threshold value for the acceleration force of the power tool and comparing the retrieved threshold value with the received parameter values relating to the acceleration force of the power tool. The method further comprises determining that the power tool has been exposed to an acceleration force greater than the threshold value based on the outcome of the comparing step.

In an embodiment the method also comprises transmitting an alarm message as response to determining that the power tool has been exposed to an acceleration force greater than the threshold value.

In another embodiment the method comprises sending a request for parameter values to the power tool, via the communication network. In yet another embodiment the method further comprises retrieving parameter values relating to a desired exposure of acceleration force of the power tool over a working cycle, comparing the retrieved parameter values relating to the desired exposure of acceleration force of the power tool over the working cycle with the received parameter values relating to the acceleration force of the power tool, and determining that the power tool has been exposed to an acceleration force that is greater than the threshold value prior to an active use of the power tool, such as tightening a bolt, and wherein in response thereto the step of transmitting an alarm message comprises indicating that the power tool probably has been used as a hammer prior to the active use of the power tool.

In a further embodiment the method comprises comparing the retrieved parameter values relating to the desired exposure of acceleration force of the power tool over the working cycle with the received parameter values relating to the acceleration force of the power tool, and determining that the power tool has been exposed to an acceleration force that is greater than the threshold value after an active use of the power tool, such as tightening a bolt, and wherein in response thereto the step of transmitting an alarm message comprises indicating that the power tool probably has been dropped after the active use of the power tool.

In another embodiment the method comprises incrementing a counter every time it is determined that the power tool has been exposed to an acceleration force that is greater than the threshold value, and in response to that a counter value exceeds a second threshold value transmitting an alarm message indicating that a predicted useful life of the power tool is coming to an end.

According to another aspect a monitoring node for monitoring usage of a power tool and associated with a tool communication network is provided. The power tool is connected to the communications network. The monitoring node comprises a processor and a memory, the memory comprising instructions which when executed by the processor causes the monitoring node to receive, from the power tool, parameter values relating to an acceleration force of the power tool, retrieve a threshold value for the acceleration force of the power tool and compare the retrieved threshold value with the received parameter values relating to the acceleration force of the power tool. The monitoring node is further caused to determine that the power tool has been exposed to an acceleration force greater than the threshold value based on the comparing step.

In an embodiment the monitoring node is further caused to transmit an alarm message as response to determining that the power tool has been exposed to an acceleration force greater than the threshold.

The monitoring node is, in another embodiment, caused to send a request for parameter values to the power tool, via the communication network.

In yet another embodiment the monitoring node is further caused to retrieve parameter values relating to a desired exposure of acceleration force of the power tool over a working cycle, compare the retrieved parameter values relating to the desired exposure of acceleration force of the power tool over the working cycle with the received parameter values relating to the acceleration force of the power tool, and determine that the power tool has been exposed to an acceleration force that is greater than the threshold value prior to an active use of the power tool, such as tightening a bolt, and wherein in response thereto the alarm message comprises an indication that the power tool probably has been used as a hammer prior to the active use of the power tool.

In another embodiment the monitoring node is further caused to compare the retrieved parameter values relating to the desired exposure of acceleration force of the power tool over the working cycle with the received parameter values relating to the acceleration force of the power tool and determine that the power tool has been exposed to an acceleration force that is greater than the threshold value after an active use of the power tool, such as tightening a bolt, and wherein in response thereto the alarm message comprises an indication that the power tool probably has been dropped after the active use of the power tool.

In a further embodiment the monitoring node comprises a counter and is caused to increment the counter every time it is determined that the power tool has been exposed to an acceleration force that is greater than the threshold value, and in response to that a counter value exceeds a second threshold value transmit an alarm message indicating that a predicted useful life the of the power tool is coming to an end.

According to another aspect, a computer program and a computer program product comprises computer readable code is provided, which when executed on a processor of the monitoring node causes the monitoring node to behave as a monitoring node described in previous sections.

Further possible features and benefits of this solution will become apparent from the detailed description below. Brief description of drawings

The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

Fig. 1 is an overview of a tool communication network.

Fig. 2 is a block diagram illustrating the monitoring node in more detail, according to possible embodiments.

Fig 3 is a flowchart of a method according to one possible embodiment.

Fig. 4 is a flowchart of the method according to other possible embodiments.

Fig. 5 is a flowchart of another possible embodiment.

Figs. 6a-c are graphs illustrating the desired and received acceleration force over time for a power tool.

Detailed description

Briefly described, a solution is provided to enable an overview of power tool usage and operator behavior at different manufacturing stations of an assembly line. In an environment where a number of power tools are used, normally controlled by controllers, the power tools may be configurable for different operations. A specific power tool may further be a part of a manufacturing station together with material for production, arrangements for material handling, different accessories or fittings for the power tool, and so forth. The power tool is part of a tool communication network. The tool communications network may be operated in a small

manufacturing plant in a clean environment. The tool communications network may be operated in a manufacturing environment distributed over several buildings or remote locations. The tool communications network may be operated in a manufacturing environment in a factory with a challenging environment of dirt, aggressive chemicals, electrical disturbances, sometimes challenging for communication equipment and computers. A suitable tool communications network for use together with the present invention is described in greater detail in PCT/EP2015/064814.

Fig. 1 shows an overview of the tool communications network 50. The tool communications network 50 may comprise power tools 125, 135, tool controllers 122, 123, a tool server 140, a communication node (hub) 150 and a monitoring node 100. In Fig. 1 three different types of monitoring nodes are shown, which will be described further below. The tool communication network 50 is set up to support different manufacturing stations 120, 130 that are part of an assembly line. Usually there are more than two manufacturing stations in an assembly line, but in Fig. 1 only two are shown in order to illustrate an explanatory tool communications network 50. Fig. 1 also shows a workpiece 1 10 having a first bolt 80 that is to be tighten at a first manufacturing station 120 and a second bolt 90 to be tighten at a second manufacturing station 130.

The power tools 125, 135 are connected with a respective tool controller 122, 123 for control, supervision and collection of result data from the power tools 125, 135. The power tools 1 25, 135 may be set up for simple operations such as tightening bolts as mentioned above. However, the power tools 125, 135 may also be set up for complex work operations including a number of similar and different operations, series of operations with one equipment, shifting to another equipment followed by another series of operations and may be shifting to a third equipment. How the power tools 125, 135 should perform operations and interact with an operator, may be based on control data received from the tool controllers 122, 123. Each individual operation may need to be performed with high accuracy in terms of e.g. torque and rotation speed. In order to maintain desirable quality control all results may be collected by sensors, such as the number of rotations, final torque, location of operation, time, and similar result data for power tool operation. The tool controllers 122, 1 23 controlling the power tools 1 25, 135 and accessory equipment have the primary task to control the power tools 1 25, 135. The tool controllers 1 22, 1 23 also manage configuration data and collect sensor data and store the sensor data as results of performed work operations. The tool controller 1 22, 1 23 may be a specific node for control of power tools 1 25, 1 35 or it may be for example a general purpose computer, which has been adapted for control of power tools. The tool controllers 122, 1 23 may be connected to the tool communication network 50 by wire as the tool controller 1 22 or wirelessly as schematically shown by tool controller 123. The tool controllers 122, 1 23 may also be termed controller, controller node, controlling node, control unit, tool processor, tool regulator, or similar terms. The tool controller 1 22, 123 may be co-located or comprised by a power tool 1 25, 1 35, a tool server 140, communication node 1 50, or other suitable technical nodes operating in a tool communications network 50.

The tool server 140 is a server to which production managers or production technicians may connect for creation and/or administration of work operations for the power tools 1 25, 1 35. The tool server 140 may be a general purpose server or a tool server 1 40 specifically arranged for remote control of power tools 1 25, 135. Administrators connecting to the tool server may for example create, specify and change how a particular power tool or a group of power tools 1 25, 135 should behave in certain situations. Examples are series of operations, tool selections, values for each operation like a torque rate, number of rotations, rotational speed, position and how to end when result data should be feed backed to a tool server 140, etc.

A communication node or hub 1 50 may be managing communication between different participating functional nodes or devices in the communications network 50. The communication node 1 50 may for example keep track of identities of tool controllers 1 22, tool servers 140, or power tools 1 25, 135. The communication node 150 may keep track of any nodes or devices alternating between "on line" and "off line". A tool controller 122 may for example not always be connected to a network for various reasons. The communication node 150 may further validate and/or authorize nodes or devices communicating in the communications network 50, such that only authorized nodes have the right to communicate with each other.

The monitoring node 100, which is configured to monitor usage of the power tools 125, 135 may be part of the tool server 140, be provided as part of a cloud solution or be provided as a stand-alone server. The monitoring node 100 is shown in greater detail in Fig. 2. The monitoring node 100 comprises a processor 350, a memory 365 and a communication interface 370 for communication with other nodes and devices in the communication tool network 50, such as the power tools 125, 135. Depending on the configuration the monitoring node 100 may further and as an option also comprise a counter 390 and a repository 375. The counter 390 may be used to predict end of life of a power tool 125, 135 which will be further explained below in conjunction with Fig. 5. The repository may comprise historic data and/or different thresholds used to determine different types of usage and operator behavior of the power tool 125, 135. Fig. 2 further shows a computer program 365 comprising computer program code. The computer program code is adapted to implement a method performed by the monitoring node 100 if executed on the processor 350. The method will be closer described in conjunction with Figs. 3 to 5. The computer program 365 may be stored on the memory 360, but may also be provided on a computer readable storage medium, such as a CD or a USB stick, that is loaded into the memory 360. Turning now to Fig. 3 a method performed by a monitoring node 100 will be described in more detail. The monitoring node 100 is associated with the tool communication network 50 for monitoring the usage of power tools 125, 135 in for example an assembly line. As mentioned above the power tools 125, 135 are also connected to the communications network 50. In a step, S100, of the method performed by the monitoring node 100, the monitoring node 100 receives, from the power tool 125, 135, parameter values relating to an acceleration force of the power tool 1 25, 1 35. As mentioned above power tools 1 25, 1 35 are provided with different types of sensors. One such type may for example be an accelerometer or gyro that is capable of recording the acceleration force that the power tool 1 25, 1 35 is exposed to. However, there may possible also be other sensors used to obtain parameter values that are associated with the acceleration force of the power tool 1 25, 1 35. What is important in the context of the present invention is that the monitoring node 100 receives parameter values that are associated with the acceleration force of the power tool 1 25, 1 35. In another step, S1 1 0, the monitoring node 1 00 retrieves a threshold value for the acceleration force of the power tool 125, 135. This step, S1 1 0, may be performed prior to or after the step, S1 00, of receiving parameter values. The threshold value may be received from the tool server 140, the cloud solution 1 60 or any other suitable node being part of or connected to the tool communication network 50. After that the receiving step, S1 00, and the retrieving step, S1 10, have been performed the monitoring node 1 00 compares in step S1 20 the retrieved threshold value with the received parameter values relating to the acceleration force of the power tool 1 25, 1 35 and determines in step S1 30 that the power tool 1 25, 1 35 has been exposed to an acceleration force greater than the threshold value based on the outcome of the comparison in step 120. The threshold value is set such that "normal" behavior of an operator operating the power tool 125, 135 does not lead to that the received parameter values exceed the threshold value. However, if the power tool 1 25, 1 35 is dropped or for example is used as a hammer the received parameter values will exceed the threshold value, which will be described closer in conjunction with Figs. 6a-c.

With reference to Fig. 4 different embodiments and variations of the method performed by the monitoring node 100 will be will be closer described. The main steps described in conjunction with Fig. 2 are repeated in Fig. 4 and are shown with unbroken lines. Optional steps and variations are shown with dashed lines in Fig. 4. In one embodiment the monitoring node 100 transmits in step S140 an alarm message in response to determining that the power tool 125, 135 has been exposed to an acceleration force greater than the threshold value. This alarm message may be sent to the tool server 140 for storage and later access by the production manager or any other authorized person. The alarm message may also be sent to any other node in the communication network 50 or to any node connected thereto. The alarm message could for example be sent directly to a smart phone or any other device capable of receiving messages as a text message. Thus, be sending the alarm message it is possible to notify for example the production manager as soon as one discovers divergent acceleration values, i.e. that a power tool 125, 135 is exposed to acceleration forces above a threshold. This gives the production manager an opportunity to go and observe how the power tool 125, 135 is used at a particular manufacturing station 120, 130 or by a particular operator. In one embodiment the parameter values received in step S100, may be received more or less continuously or with regular intervals that are preprogrammed either in the power tool 125, 135 or in the tool controller 122, 123 controlling the power tool 125, 135. In another embodiment the parameter values are only received when requested by the monitoring node 100. Thus, in step S100A the monitoring node 100 sends a request for parameter values to the power tool 125, 135, via the communication network 50.

In another optional step, S105, of the method the monitoring node 100 retrieves parameter values relating to a desired exposure of acceleration force of the power tool 125, 1 35 over a working cycle. A working cycle is the time that a workpiece 1 10 spends at a manufacturing station 120 before it is moved to the next manufacturing station 120 of the assembly line, i.e. the time it takes for the operator to perform the process steps at a manufacturing station, for example tightening two bolts. A working cycle is often less than 5 minutes. The desired exposure of the acceleration force is the acceleration force that the power tool 125, 135 normally is exposed to, i.e. when everything is running smoothly. An exemplary acceleration force curve with a desired motion pattern for a working cycle is shown in Fig. 6a. As may be seen the acceleration force curve in Fig. 6a has two humps A and B. These two humps A, B indicate an increase of the acceleration force during a working cycle. The humps A, B are relatively low and correspond to two operation steps when the operator lifts and operates the power tool 125, 135 to for example tighten two bolts.

The desired motion pattern is very useful for determining different types of operator behavior. Thus, in step S125 the monitoring mode compares the retrieved parameter values relating to the desired exposure of acceleration force of the power tool 125, 135 over the working cycle with the received parameter values relating to the acceleration force of the power tool 125, 135. The received parameter values may for example correspond to current motion pattern 1 that is shown in Fig. 6b. Based on this current motion pattern 1 the monitoring node 100 determines in step S138 that the power tool 125, 135 has been exposed to an acceleration force that is greater than the threshold value after an active use of the power tool 125, 135 such as tightening a bolt. In Fig. 6b this may be seen as a peak C that occurs after each hump A and B, i.e. after that an operator has performed the work steps with the power tool 125, 135. Thus, something out of the ordinary happens with the power tool 125, 135 after the operator has performed his operations. In response to determining that and when the threshold value for the acceleration force has been exceeded the step of transmitting S140 an alarm message comprises indicating that the power tool 125, 135 probably has been dropped after the active use of the power tool 125, 135. There may be different reasons for this occurrence. One scenario is that the operator deliberately drops the power tool 125, 135 after each operation or there may be a broken power tool holder such that the power tool is accidently dropped. Since the monitoring node

100 sends the alarm message it is now possible for someone, like the production technician to observe the manufacturing station in question in order to determine the reason why the threshold value has been exceeded.

In another embodiment the received parameter values may for example

correspond to current motion pattern 2 that is shown in Fig. 6c. Based on this current motion pattern 2 the monitoring node 100 determines in step S135 that the power tool 125, 135 has been exposed to an acceleration force that is greater than the threshold value prior to an active use of the power tool 125, 135, such as tightening a bolt. This may be seen in Fig. 6c by three peaks exceeding the threshold value T, collectively denoted D, prior to hump B. Thus, also in this case something out of the ordinary happens with the power tool 125, 135, but now prior to the operation of the operator. In response to determining that and when the threshold value for the acceleration force has been exceeded the step of transmitting S140 an alarm message comprises indicating that the power tool 125, 135 probably has been used as a hammer prior to the active use of the power tool 125, 135. This conclusion is based on that the threshold value T repeatedly has been exceeded prior to the use of the power tool 125, 135. There may be different reasons for this occurrence. One scenario is that the for example a bolt does not fit properly due to irregulars of the workpiece or variations in the properties of the bolt. Since the monitoring node 100 sends the alarm message it is now possible for someone, like the production technician to observe the manufacturing station in question in order to determine the reason why the threshold value has been exceeded.

Turning now to Fig. 5 yet another embodiment will be described. When it has been determined that the parameter values received at the monitoring node 100 have exceeded the threshold value a counter 390 will be incremented at step S150. Thereafter a check is made to determine if the counter value exceeds a second threshold value. If it is determined that the second threshold has been exceeded an alarm message is transmitted in step S1 60. For example if the power tool 125, 135 has been dropped for example 50 times there might be a high probability that the power tool soon will be broken. Thus, the alarm message is transmitted with an indication that a predicted useful life of the power tool is coming to an end. This is very useful, since substituting worn out power tools before they fail with new power tools will reduce downtime of the assembly line and increase productivity.

Turning now to Fig. 2 again the functioning of the monitoring node 100 will be described closer. As mentioned above the monitoring node 100 is associated with the tool communication network 50, for monitoring usage of the power tools 125, 135 and comprises the processor 350 and the memory 360. The memory 360 comprises instructions which when executed by the processor 350 causes the monitoring node 100 to receive, from the power tools 125, 135, parameter values relating to an acceleration force of the power tools 125, 135, retrieve a threshold value for the acceleration force of the power tools 125, 135 and compare the retrieved threshold value with the received parameter values relating to the acceleration force of the power tools 125, 135. The monitoring node 100 is further caused to determine that the power tool 125, 135 has been exposed to an acceleration force greater than the threshold value based on the outcome of the comparing step.

It should be understood that the monitoring node 100 is further configured to execute the computer program code of the computer program 365 such that the monitoring node 100 is caused to perform all of the method steps or actions described above in conjunction with Figs. 3-5. Thus, these steps are not repeated here.

The processor 350 may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units. For example, the processor 350 may include general purpose microprocessors, instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or Complex Programmable Logic Devices (CPLDs). The processor 350 may also comprise a storage for caching purposes.

The computer program may be carried by computer program products in the described monitoring node 100, in the form of memories having a computer readable medium and being connected to the processor 350. The computer program products may be carried by a medium, such as CD, DVD, flash memory, or downloadable objects. Each computer program product or memory thus comprises a computer readable medium on which the computer program is stored e.g. in the form of computer program units. For example, the memories may be a flash memory, a Random-Access Memory (RAM), a Read-Only Memory (ROM) or an Electrically Erasable Programmable ROM (EEPROM), and the program unit's u could in alternative embodiments be distributed on different computer program products in the form of memories within the described monitoring node 100 or within the tool communication network 50.

While the solution has been described with reference to specific exemplary embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms "tool communications network", "monitoring node", "tool server", "power tool" and "tool controller" have been used throughout this description, although any other corresponding nodes, functions, and/or parameters could also be used having the features and characteristics described here. The solution is defined by the appended claims.