SE545131C2

SE545131C2 - Method of determining fastener length, electronic control system and tool

Info

Publication number: SE545131C2
Application number: SE2130367A
Authority: SE
Inventors: Erik Persson; Sofia Olsson
Original assignee: Atlas Copco Ind Technique Ab
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2023-04-11
Also published as: SE2130367A1

Abstract

A method of determining a length (30a, 30b) of a fastener (12), the method comprising providing a tool (10a; 10b) including a socket (14), and a sensor device (16a; 16b); receiving, by the sensor device (16a; 16b), radiation from the fastener (12) when the fastener (12) is received in the socket (14); issuing, by the sensor device (16a; 16b), electronic data (40) based on the received radiation; and determining, by an electronic control system (34), the length (30a, 30b) of the fastener (12) based on the electronic data (40). An electronic control system (34) for determining a length (30a, 30b) of a fastener (12) and a tool (10a; 10b) are also provided.

Description

METHOD OF DETERMINING FASTENER LENGTH, ELECTRONIC CONTROL SYSTEM AND TOOL Technical Field The present disclosure generally relates to length determination of fasteners. In particular, a method of determining a length of a fastener, an electronic control system for determining a length of a fastener, and a tool, are provided. Background Tools for applying fasteners to joints, such as torque wrenches, are widely used in the manufacturing industry, for example in vehicle manufacturing and in the aerospace industry. In some applications, an operator has fasteners of different lengths at disposal for a particular joint. In this case, there is a risk that the operator applies a fastener of erroneous length to the joint.

Although technologies for measuring the length of a fastener exist, prior art solutions are expensive, space demanding and complicated. Furthermore, with prior art solutions, the operator may still select a fastener of erroneous length despite the lengths of several fasteners have been measured. Summary One object of the present disclosure is to provide an improved method of determining a length of a fastener.

A further object of the present disclosure is to provide a method of determining a length of a fastener, which method reduces or eliminates a risk that a joint is assembled with a fastener of incorrect length.

A still further object of the present disclosure is to provide a reliable method of determining a length of a fastener.

A still further object of the present disclosure is to provide a method of determining a length of a fastener, which method can easily be implemented in an existing tool.

A still further object of the present disclosure is to provide a method of determining a length of a fastener, which enables a foolproof use of the tool.

A still further method of the present disclosure is to provide a method of determining a length of a fastener, which method solves several or all of the foregoing objects in combination.

A still further object of the present disclosure is to provide an electronic control system for determining a length of a fastener, which control system solves one, several or all of the foregoing objects.

A still further object of the present disclosure is to provide a tool solving one, several or all of the foregoing objects.

According to a first aspect, there is provided a method of determining a length of a fastener, the method comprising providing a tool including a socket and a sensor device; receiving, by the sensor device, radiation from the fastener when the fastener is received in the socket; issuing, by the sensor device, electronic data based on the received radiation; and determining, by an electronic control system, the length of the fastener based on the electronic data. The method further comprises determining whether the length is correct, and informing the operator of whether the length is correct.

By determining the length of the fastener when the fastener is received in the socket, in contrast to determining the length of the fastener prior to putting the fastener in the socket, a risk of assembling a joint with a fastener having an incorrect length can be eliminated. This risk has previously been occurring when an operator has to select a fastener between two fasteners having the same diameter but different lengths. Thus, although the lengths of both fasteners may be known, there is still a risk that the operator puts the fastener with the erroneous length into the socket. The fastener with the incorrect length can threadingly engage a target hole without the operator necessarily noticing the incorrect length. The feature of the method that the length is determined at a very late stage, i.e. after the selected fastener has actually been put into the socket, is therefore very advantageous. In this way, a foolproof operation of the tool is enabled.

A further advantage with the method is that an operator of the tool does not have to check the length of the fastener before putting the fastener in the socket. The method further enables elimination of any external devices for determining whether the length of the fastener is correct, such as templates or guides. The determination of the length may comprise determining an absolute length of the fastener.

With the present aspect, the method also adds simplicity since the operator is informed regarding whether a correct fastener has been placed in the socket.

Throughout the present disclosure, the fastener may be configured to mechanically join two or more members. The fastener may be a threaded fastener, such as a bolt or a screw. Examples of unthreaded fasteners comprise nails and rivets.

The tool may comprise a housing. The tool may further comprise one or more magnets configured to hold the fastener in the socket.

The socket may be be detachably connected to the tool. The socket may for example be provided in a tool head detachably connected to the housing. The socket may or may not be rotatable relative to the housing. The socket may be configured to receive a head of the fastener.

The sensor device is in signal communication with the control system, either wired or wirelessly. The sensor device may be provided inside the housing, or inside a tool head. The sensor device may be provided in the socket. The radiation may be sound waves or electromagnetic radiation. The control system may or may not be provided in the tool.

The method may comprise providing the information whether the length is correct to the operator by visual, audible or tactile feedback, for example from the tool or from an external device associated with the tool.

The method may comprise comparing the determined length with a reference length for the fastener. In case the determined length differs from the reference length, for example with more than 0.2 %, such as with more that 1 %, such as with more than 2 %, it may be concluded that the determined length is incorrect.

The reference length may be provided in various ways. The reference length may be determined based on a location of the tool. A first reference length may be associated with a first location and a second reference length, different from the first reference length, may be associated with a second location, different from the first location. When the tool is located at the first location, the determined length is compared with the first reference length. When the tool is located at the second location, the determined length is compared with second reference length.

Alternatively, or in addition, the reference length may be determined based on a task of the tool. A first reference length may be associated with a first task and a second reference length, different from the first reference length, may be associated with a second task, different from the first task. When the tool is to perform the first task, the determined length is compared with the first reference length. When the tool is to perform the second task, the determined length is compared with second reference length.

The task of the tool can be determined in various ways. In one example, a first task is associated with a first work object and a second task is associated with a second work object, different from the first work object. Examples of work objects comprise vehicles of different types.

Alternatively, or in addition, the reference length may be included in a set of parameters that controls a tightening operation, or other assembly operation using the fastener. This set of parameters may be referred to as a Pset. In some variants, a certain Pset can only be used at a specific location of the tool. The Pset may be selected by the operator or may be automatically selected. The Pset may for example be associated with the socket. When the socket is changed, a new Pset is selected.

Alternatively, or in addition, the reference length may be determined based on a sequence of tightening operations, or other assembly operations using fasteners. For example, the operator can be expected to tighten fasteners of different lengths in a specific sequence. The reference length may thus be determined based on how many tightening operations of the sequence that have been completed.

The method may further comprise commanding, by the control system, a countermeasure upon determining that the length is incorrect. In this way, a risk of assembling a joint with a fastener having incorrect length is eliminated. Examples of countermeasures comprise a visual, audible and/ or tactile feedback, for example from the tool or from an external device associated with the tool. The method may comprise preventing assembly with the fastener in the socket upon determining that the length is incorrect, and allowing assembly with the fastener in the socket upon determining that the length is correct.

The tool may comprise a motor arranged to rotationally drive the socket. The motor may be an electric motor. The tool may further comprise a transmission arranged to transmit a rotation of an output shaft of the motor to a rotation of the socket. The transmission may comprise one or more gear wheels. The method may further comprise preventing, by the control system, the motor from rotationally driving the socket upon determining that the length is incorrect.

The tool may however be a manually operated tool. In this case, the tool does not have to comprise a motor. One example of such tool is a click wrench.

A first length of the fastener may be determined prior to a tightening operation of the fastener by the tool. A second length of the fastener may be determined after the tightening operation. In this case, the method may further comprise determining a difference between the first length and the second length. When a threaded fastener is tightened in a joint, tension is introduced in the fastener and the fastener is elongated. The elongation is proportional to the tension. The method may further comprise determining the clamp load in the tightened fastener based on the difference between the first length and the second length, e.g. by using Hooke's law.

The radiation may comprise ultrasonic waves. The method thus enables fastener length recognition using ultrasonic radiation. The use of ultrasound enables the sensor device to be small and to be placed in the socket. The use of a sensor device in the socket is advantageous since the risk that the operator uses a fastener with undetermined length can thereby be eliminated.

The sensor device may comprise an ultrasonic transceiver, or a pair of an ultrasonic transmitter and an ultrasonic receiver. The transceiver or the transmitter may comprise a piezoelectric chip configured to generate ultrasonic waves in response to electrical control signals from the control system. The tool may further comprise a resilient contact layer, such as a dry or gel-formed membrane, that is brought into direct contact with a head of the fastener. The transceiver or the receiver may be configured to generate electrical response signals as the electronic data in response to the received ultrasonic waves. The response signals are then evaluated to determine the length of the fastener.

The tool may further comprise a spring arranged to force the contact layer onto the head. The tool may further comprise one or more magnets configured to hold the fastener in the socket against the force of the spring.

Some tools already comprise an ultrasonic transceiver configured to convert electrical signals to ultrasound sent through the fastener, and to convert ultrasonic echoes having interacted with the transceiver into electrical response signals as electronic data. By measuring the time of ﬂight of the ultrasonic waves back and forth through the fastener, it is possible to determine a clamp load in a joint obtained by the fastener after a completed tightening operation. The method according to this variant can be performed by only changing the software in a control system of the tool to also determine the length of the fastener based on times of ﬂight of the ultrasonic WEIVGS.

In comparison with determining the clamp load of the fastener with a single measurement, the determination of the length of the fastener can be made in a less complicated way. For example, the pressure of the contact layer onto the head does not have to be as even when measuring length of a fastener as when measuring clamp load of the fastener. This enables the hardware of the tool to be less complex. For example, since the length of the fastener can be measured either before or after a tightening operation, the ultrasonic transceiver does not have to be suspended to withstand vibrations during the tightening operation. The suspension of the sensor device can therefore be made less complicated. The clamp load determined based on the difference between the first length and the second length can be used to verify a clamp load measured in another way, such as with ultrasonic radiation. The accuracy of a clamp load measurement can thereby be increased.

According to one variant, the tool is configured to repeatedly try to measure the length, for example at least one time per second, such as at least ten times per second. In case no fastener is put into the socket, no reﬂected ultrasonic waves will be received. It can then be concluded that no fastener is present in the socket. Since in this way it can be detected when a fastener is removed from the socket, a risk that the fastener is replaced with a fastener with undetermined or erroneous length after length measurement, and that this erroneous fastener is then assembled in a joint, can thereby be eliminated.

According to one possible alternative variant, the tool may comprise an imaging device, such as a 3D camera, configured to determine the length of the fastener when received in the socket. Thus, the radiation from the fastener may be electromagnetic radiation.

The method may further comprise determining, by a temperature sensor, a temperature value indicative of a temperature of the fastener. In this case, the length may be determined also based on the temperature value. The speed of sound changes with changing temperature. By taking the temperature into consideration, the correct speed of sound is known and the absolute length of the fastener can be determined with ultrasound. The temperature sensor may be provided in the tool or outside the tool. As a possible alternative, it may be assumed that the temperature is constant, e.g. at room temperature (20 °C).

According to a second aspect, there is provided an electronic control system for determining a length of a fastener received in a socket of a tool, where the tool comprises the socket and a sensor device, the control system comprising at least one data processing device and at least one memory having at least one computer program stored thereon, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform the steps of receiving, from the sensor device, electronic data based on received radiation from the fastener by the sensor device when the fastener is received in the socket; and determining the length of the fastener based on the electronic data.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform, or command performance of, any step described herein.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to determine whether the length is correct, and informing the operator of whether the length is correct.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to command a countermeasure upon determining that the length is incorrect.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to determine a first length of the fastener prior to a tightening operation of the fastener by the tool, and determine a second length of the fastener after the tightening operation.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to determine a difference between the first length and the second length.

The radiation may comprise ultrasonic waves. In this case, the at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to send electrical control signals to the sensor device to thereby generate ultrasonic waves in response.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to provide, from a temperature sensor, a temperature value indicative of a temperature of the fastener, and determine the length also based on the temperature value.

According to a third aspect, there is provided a tool comprising the socket; the sensor device; and the control system according to the second aspect. The tool according to the third aspect may be of any type as described in connection with the first aspect, and vice versa.

The tool may be a tool for applying a fastener, such as tightening tool. The tool may for example be a nutrunner, a torque wrench or a screwdriver. The tool may be handheld.

The sensor device may be an ultrasonic sensor device configured to send ultrasonic waves to the fastener, sense echo signals induced in the fastener, and convert the echoes to the electronic data. The tool may comprise a motor arranged to rotationally drive the socket.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to prevent the motor from rotationally driving the socket upon determining that the length is incorrect. Brief Description of the Drawings Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein: Fig. 1: schematically represents a side view of a tool and a fastener; Fig. 2: schematically represents a side view of the tool when the fastener is received in a socket of the tool; Fig. 3: schematically represents a side view of the tool when the fastener has been tightened; andFig. 4: schematically represents a side view of a further example of a tool and the fastener. Detailed Description In the following, a method of determining a length of a fastener, an electronic control system for determining a length of a fastener, and a tool, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

Fig. 1 schematically represents a side view of a tightening tool 1oa and a fastener 12. The tightening tool 1oa is one example of a tool according to the present disclosure. The tightening tool 1oa is handheld and configured to apply the fastener 12 to mechanically join two or more mechanical members. The tightening tool 1oa comprises a socket 14 and an ultrasonic transceiver 16a. The ultrasonic transceiver 16a is one example of a sensor device according to the present disclosure. The ultrasonic transceiver 16a of this example comprises a resilient contact layer 18, here exemplified as a dry membrane.

The fastener 12 of this example is a threaded bolt comprising a head 20, a fastener shaft 22, a proximal surface 24 on the head 2o, and a distal surface 26 on the fastener shaft 22. In this example, each of the proximal surface 24 and the distal surface 26 is ﬂat and transverse to a longitudinal axis 28 of the fastener 12. Fig. 1 further shows a first length 3oa of the fastener 12 from the proximal surface 24 to the distal surface 26 in parallel with the longitudinal axis 28. The first length 3oa is a length of the fastener 12 in an undeformed state prior to a tightening operation. The fastener 12 may for example be made of steel.

The tightening tool 1oa further comprises a housing 32. The socket 14 of this example is detachably connected to the tightening tool 1oa and can rotate relative to the housingThe tightening tool 1oa of this example further comprises a control system 34. The control system 34 comprises a data processing device 36 and a memory 38. The memory 38 has a computer program stored thereon. The computer program comprises program code which, when executed by the data processing device 36, causes the data processing device 36 to perform, or command performance of, various steps according to the present disclosure.

The ultrasonic transceiver 16a is in signal communication with the control system 34. The control system 34 is configured to send electrical control signals to the ultrasonic transceiver 16a. The ultrasonic transceiver 16a of this example comprises a piezoelectric chip configured to generate ultrasonic waves in response to the electrical control signals. The ultrasonic transceiver 16a is further configured to generate electronic data 40 in response to received ultrasonic waves. Ultrasonic waves are examples of sound radiation according to the present disclosure.

The tightening tool 1oa of this example further comprises an electric motor 42. The motor 42 comprises a motor output shaft 44. The motor 42 is controlled by the control system The tightening tool 1oa of this example further comprises a gearbox 46. The gearbox 46 comprises a gearbox output shaft 48. The gearbox 46 of this example is a speed decreasing gearbox configured to transmit a rotation of the motor output shaft 44 at a first rotational speed to a rotation of the gearbox output shaft 48 at a second rotational speed, lower than the first rotational speed.

The tightening tool 1oa of this example further comprises a drive shaft 50. The drive shaft 50 is rotationally driven by rotation of the gearbox output shaft 48, here via intermediate bevel gears. The socket 14 may be detachably connectable to the drive shaft 50. By driving the motor 42, the socket 14 is rotationally driven. The gearbox 46 and the bevel gears thus constitute oneexample of a transmission arranged to transmit a rotation of the motor output shaft 44 to a rotation of the socket The tightening tool 10a of this example further comprises a driving command element, here exemplified as a lever 52 hingedly connected to the housing 32. The lever 52 is in signal communication with the control system 34. The control system 34 may command rotation of the motor 42 in response to actuation of the lever The tightening tool 10a of this example further comprises a display 54. The display 54 is here positioned on the housing 32. The control system 34 is configured to control display of various information related to the tightening tool 10a and/ or the fastener 12 on the display The tightening tool 10a of this example further comprises a temperature sensor 56. The temperature sensor 56 is in signal communication with the control system 34. The temperature sensor 56 is configured to determine a temperature value 58 and to send this temperature value 58 to the control system 34. The temperature value 58 is indicative of a temperature measured by the temperature sensor 56. The temperature sensor 56 may alternatively be positioned remote from the tightening tool 10a.

The tightening tool 10a of this example further comprises a spring 60. The spring 60 is arranged to force the ultrasonic transceiver 16a into the socket 14. As shown in Fig. 1, the ultrasonic transceiver 16a of this example is very small and is positioned radially inside the socket 14 with respect to a rotation axis of the socket 14. The spring 60 is here exemplified as a compression coil spring. In Fig. 1, the spring 60 is in an undeformed state.

The socket 14 of this example comprises magnets 62. The magnets 62 are here positioned in a bottom of the socket 14 and are configured to magnetically force the head 20 the into the bottom.In the tightening tool 1oa of this example, the control system 34 repeatedly commands the ultrasonic transceiver 16a to generate ultrasonic waves, for example ten times per second. Since ultrasonic waves are not reﬂected, or are not reﬂected in a manner corresponding to when a fastener 12 is received in the socket 14, the control system 34 can conclude that no fastener 12 is put into the socket Fig. 2 schematically represents a side view of the tightening tool 1oa. In Fig. 2, an operator has put the fastener 12 into the socket 14. The magnets 62 hold the fastener 12 in the socket 14 against the force of the spring 60. As shown in Fig. 2, this causes the spring 60 to be compressed. As a consequence, the contact layer 18 is forced against the proximal surface 24 of head 20 of the fastener The ultrasonic waves generated by the ultrasonic transceiver 16a now travels through the fastener 12 from the proximal surface 24 to the distal surface 26. At the distal surface 26, the ultrasonic waves are reﬂected to travel back through the fastener 12 to the proximal surface 24 where the reﬂected ultrasonic waves are received by the ultrasonic transceiver 16a and converted to electronic data 40 sent to the control system 34. The first length 3oa can be determined as an absolute length based on the following formula: AIS Lfastener I Cs * ï (1) where Lfastenef [m] is the first length 3oa of the fastener 12, cs [m/ s] is the speed of sound through the material of the fastener 12 and At [s] is the time until the ultrasonic echo returns. By also taking into account the temperature value 58 indicative of the temperature from the temperature sensor 56, the speed of sound can be determined accurately. In order to measure a first length 3oa of a fastener having a concave head, the ultrasonic transceiver 16a may be offset from the rotation axis of the socket The control system 34 of this example then determines whether the first length 3oa is correct. In this example, the control system 34 has provided a reference length for the fastener 12. The reference length may be provided in many different ways.

The reference length may for example be determined based on a location of the tightening tool 1oa. The location of the tightening tool 1oa can be determined in various ways. According to one example, the location of the tightening tool 1oa is determined based on triangulation. Alternatively, or in addition, the location of the tightening tool 1oa can be determined by using Bluetooth, UWB (ultra-wideband) and/ or a vision system. A vision system may for example be positioned in a ceiling at an assembly site. The vision system may be configured to identify a feature on the tightening tool 1oa, such as a mark, and/ or a feature on a work object, and determine a location of the tightening tool 1oa in relation to the work object.

The reference length may alternatively or additionally be determined based on a task of the tightening tool 1oa and/ or an identity of a work object. For example, a first reference length may be set for a first type of work object and a second reference length may be set for a second type of work object.

The reference length may alternatively or additionally be included in a so- called Pset, i.e. a set of parameters associated with a tightening operation. Alternatively, or in addition, the reference length may be determined based on where the tightening operation is in a sequence of a plurality of tightening operations. In some situations, the operator can be expected to apply fasteners 12 in a specific order. This order can relied upon to provide a reference length for each tightening operation.

Regardless of how the reference length is provided, the control system 34 compares the first length 3oa with the reference length. If for example the first length 3oa differs with more than 1 % from the reference length, the control system 34 may conclude that the first length 3oa is incorrect. Thereference length of the fastener 12 may for example be 50 mm. If the determined first length 3oa differs with 1 mm from the reference length, the first length 3oa may be determined to be incorrect.

In case the first length 3oa is incorrect, the control system 34 commands issuance of information of this incorrectness to the operator. In this specific example, the control system 34 may command the display 54 to display a red light indicating that the first length 3oa is incorrect. This type of display constitutes one example of a countermeasure according to the present disclosure. The operator thereby becomes aware of this incorrectness and should avoid applying the fastener 12 to the joint. However, the control system 34 of this example also prevents the motor 42 to be driven when the lever 52 is actuated upon determining that the first length 3oa of the fastener 12 held in the socket 14 is incorrect. In this way, it is made impossible for the operator to apply the fastener 12 of incorrect length to the joint.

If the first length 3oa of the fastener 12 is incorrect and the operator replaces the fastener 12 with a further fastener, the first length 3oa of the further fastener is measured and the above steps are repeated.

If the first length 3oa of the fastener 12 is correct, the control system 34 of this example commands issuance of information of this correctness to the operator. In this specific example, the control system 34 may command the display 54 to display a green light indicating that the first length 3oa is correct. The operator thereby becomes aware that the fastener 12 held in the socket 14 is of correct length. Moreover, the control system 34 of this example allows the motor 42 to be driven when the lever 52 is actuated upon determining that the first length 3oa of the fastener 12 held in the socket 14 is correct. The operator can therefore now apply the fastener 12 to the joint using the tightening tool 1oa. The method as described eliminates a risk of assembling a joint using a fastener 12 of incorrect length. Moreover, the operator does not have to control the length of the fastener 12 before putting the fastener 12 into the socketFig. 3 schematically represents a side view of the tightening tool 1oa. In Fig. 3, the fastener 12 been tightened to a joint comprising a first mechanical member 64 and a second mechanical member 66. In this specific example, the fastener 12 passes through a hole in the first mechanical member 64 and threadingly engages a hole in the second mechanical member As the fastener 12 is tightened, the fastener 12 is elongated due to stresses introduced into the fastener 12. The tightening tool 1oa of this example continues to repeatedly measure the length of the fastener 12 in the manner as described above. When the tightening is completed, the control system 34 determines a second length 3ob of the fastener 12 in the same way as the first length 3oa is determined. The control system 34 then determines a difference between the first length 3oa and the second length 3ob. Based on this difference, a clamp load applied to the joint by the fastener 12 can be determined.

Fig. 4 schematically represents a side view of a further example of a tightening tool 1ob and the fastener 12. The tightening tool 1ob differs from the tightening tool 1oa by comprising a 3D camera 16b instead of the ultrasonic transceiver 16a. The 3D camera 16b is a further example of a sensor device according to the present disclosure. The 3D camera 16b of this example is fixed to the housing 32. The 3D camera 16b takes images of the fastener 12 when held in the socket 14 and sends corresponding electronic data 40 to the control system 34. The control system 34 performs image processing to determine the first length 3oa of the fastener While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.

Claims

1.A method of determining a length (3oa, 3ob) of a fastener (12), the method comprising: - providing a tool (1oa; 1ob) including a socket (14) and a sensor device (16a; 16b); - receiving, by the sensor device (16a; 16b), radiation from the fastener (12) when the fastener (12) is received in the socket (14); - issuing, by the sensor device (16a; 16b), electronic data (40) based on the received radiation; and - determining, by an electronic control system (34), the length (3oa, 3ob) of the fastener (12) based on the electronic data (4o)_;_a¿r¿¿i_ » (leterniininﬂ whether the length; íätëa. *wifi is correct, alid infforming an onerator of vvhethet* the length fffaha. “àobl is correct.

2.The method according to claim 21, further comprising commanding, by the control system (34), a countermeasure upon determining that the length (3oa, 3ob) is incorrect.

3.The method according to any of the preceding claims, wherein the tool (1oa; 1ob) comprises a motor (42) arranged to rotationally drive the socket (14).

4.The method according to claim 43, further comprising preventing, by the control system (34), the motor (42) from rotationally driving the socket (14) upon determining that the length (3oa, 3ob) is incorrect.

5.The method according to any of the preceding claims, wherein a first length (3oa) of the fastener (12) is determined prior to a tightening operation of the fastener (12) by the tool (1oa; 1ob), and a second length (gob) of the fastener (12) is determined after the tightening operation.

6.The method according to claim 54%, further comprising determining a difference between the first length (goa) and the second length (gob).

7.The method according to any of the preceding claims, wherein the radiation comprises ultrasonic waves.

8.The method according to any of the preceding claims, further comprising determining, by a temperature sensor (56), a temperature value (58) indicative of a temperature of the fastener (12), wherein the length (goa, gob) is determined also based on the temperature value (58)

9.An electronic control system (g4) for determining a length (goa, gob) of a fastener (12) received in a socket (14) of a tool (1oa; 1ob), where the tool (1oa; 1ob) comprises the socket (14), and a sensor device (16a; 16b), the control system (g4) comprising at least one data processing device (g6) and at least one memory (g8) having at least one computer program stored thereon, the at least one computer program comprising program code which, when executed by the at least one data processing device (g6), causes the at least one data processing device (g6) to perform the steps of: - receiving, from the sensor device (16a; 16b), electronic data (40) based on received radiation from the fastener (12) by the sensor device (16a; 16b) when the fastener (12) is received in the socket (14); and - determining the length (goa, gob) of the fastener (12) based on the electronic data (40) - deterrnitriïng sftfhethet' the length (fatta. gob) is correct. and informing an opcfraiçor of whether' the length ífšﬁa f-äob) is correct; e.orreet--arr-d--i-iaåbrﬁëi-iag-aﬁ-eïaereaterf--ofafxfheth-eif-*the-length(fyítaï-g-Gbš--isi _, __. . _ 5 æægjgThe control system (34) according to claim 53%, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to command a countermeasure upon determining that the length (3oa, 3ob) is incorrect.

10. The control system (34) according to any of claims to wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to determine a first length (3oa) of the fastener (12) prior to a tightening operation of the fastener 15 (12) by the tool (1oa; 1ob), and determine a second length (3ob) of the fastener (12) after the tightening operation. mg. The control system (34) according to claim æfjlylï, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (36), causes the at least one 20 data processing device (36) to determine a difference between the first length (3oa) and the second length (3ob). | The control system (34) according to any of claims wgto mg, wherein the radiation comprises ultrasonic waves. | The control system (34) according to any of claims »tekgwto wherein 25 the at least one computer program comprises program code which, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to provide, from a temperature sensor (56), a temperature value (58) indicative of a temperature of the fastener (12), and determine the length (3oa, 3ob) also based on the temperature value (58). Atool (1oa; 1ob) comprising: - the socket (14); 5 - the sensor device (16a; 16b); and - the control system (34) according to any of claims æg to fråggThe tool (1oa; 1ob) according to claim rygg, wherein the sensor device (16a; 16b) is an ultrasonic sensor device (16a) configured to send ultrasonic waves to the fastener (12), sense echo signals induced in the 10 fastener (12), and convert the echoes to the electronic data (40). The tool (1oa; 1ob) according to claim *fæﬁor æêš-gg, wherein the tool (1oa; 1ob) comprises a motor (42) arranged to rotationally drive the socket (14). The tool (1oa; 1ob) according to claimwherein the at least one computer program comprises program code which, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to prevent the motor (42) from rotationally driving the socket (14) upon determining that the length (3oa, 3ob) is incorrect.