Control of pulse tool motors using upper and lower limits

Abstract

A method for controlling the motor of a pulse tool is provided. This method includes the steps of: determining a parameter value indicating the torque and / or angle increase achieved by the pulse (n) just performed; determining a motor output control parameter value (M) for the next pulse (n+1) based on the determined parameter value (d) indicating the torque and / or angle increase, such that the motor output control parameter value is maintained between an upper limit (Mmax) and a lower limit (Mmin); and controlling the motor according to the determined motor output control parameter value to produce the next pulse. Furthermore, the upper and lower limits are set to converge toward a preset final target window (Mw) that defines an allowable range in which the motor output control parameter value for the last pulse of the tightening operation is included. This provides a tightening torque with less spread.

Description

[Technical Field]

[0001] This invention generally relates to the field of controlling the motor of a pulse tool. More specifically, this invention relates to a pulse strategy for such a pulse tool. [Background technology]

[0002] In industrial assembly, operator ergonomic requirements and the precision of tightening torque at joints are extremely important. Therefore, so-called pulse tools are often used. Pulse tools supply tightening torque in pulses, with zero output torque between each torque pulse. This is achieved by a hydraulic pulse unit that intermittently couples the motor to the output shaft, or by pulsed driving of the tool's motor itself. Such pulse tools are known for achieving high-precision tightening torque and low reaction force to the operator due to the pulse technology.

[0003] Another requirement in industrial assembly is a rapid tightening action, which saves assembly time (and therefore cost). This requirement often conflicts with the requirement for high precision in tightening torque. To speed up the tightening action, high motor power is required. However, high motor power can lead to a decrease in the accuracy of the tightening torque. In conventional pulse tools, the same motor power (and therefore the same energy) is used for pulses throughout the entire tightening action.

[0004] International Publication No. 2021151674 discloses a pulse tool in which the user can set different power levels to be used at different stages of tightening. Thus, the user can adjust the power level so that it is high in the initial stages of tightening up to a specific torque threshold, and then decreases as the torque exceeds that threshold, so that tightening is performed with low power near the target torque. Therefore, when setting the pulse output up to a specific torque threshold, the user can take into account the characteristics of the joint. It is possible to adapt the power to tighten the joint as quickly as possible up to the specific torque threshold. Furthermore, since the output can be set to a low value close to the target torque, it is also possible to achieve more precise tightening. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021151674 [Overview of the project] [Problems that the invention aims to solve]

[0006] The drawbacks of this solution are that it requires manual input and knowledge of the characteristics of the joints to which the strategy is applied. Furthermore, the preset output levels are not necessarily optimal for all joints being tightened in terms of speed and accuracy. [Means for solving the problem]

[0007] It would be advantageous to provide methods and control devices that eliminate or at least mitigate the aforementioned drawbacks. More specifically, it would be desirable to provide methods and control devices that enable better adjustment of the trade-off between the tightening speed and precision of different joints.

[0008] To better address one or more of these problems, a method and control device having the features defined in the independent claim are provided. Preferred embodiments are defined in the dependent claims.

[0009] Accordingly, according to one embodiment, a method for controlling the motor of a pulse tool is provided. The pulse tool is configured to supply torque in pulses during a tightening operation to tighten a screw joint. This method, The steps include determining parameter values ​​that indicate the torque and / or angle increase achieved by the pulse just executed, The steps include determining, based on the determined parameter values ​​indicating torque and / or angle increase, motor output control parameter values ​​for the next pulse such that the motor output control parameter values ​​are maintained between an upper limit and a lower limit, The steps include controlling the motor according to the determined motor output control parameter value and generating the next pulse, The steps are repeated until the target torque and / or target angle is reached (until the tightening operation is complete), Includes.

[0010] Furthermore, the upper and lower limits are set to converge toward a preset final target window that defines the tolerance range, and the motor output control parameter values ​​for the final pulse of the tightening operation are included within the final target window.

[0011] According to this aspect, the motor is controlled to output power in the next (i.e., immediately following) pulse depending on the torque and / or angle increase achieved by the pulse that has just been executed (i.e., the immediately preceding pulse). Thereby, a control method is provided for adjusting the output (energy) of the motor during tightening depending on the characteristics of the joint. This enables a trade-off between the speed and accuracy of tightening according to the joint to be tightened. For example, a soft joint exhibits a smaller torque increase per pulse and a larger angle increase compared to a hard joint. Due to the relatively small torque increase steps, soft joints typically may take longer to tighten. The control method can detect this and determine the motor output control parameter value to bring about an increase in the motor output in the next pulse. In this way, the tightening progresses faster compared to the case where the motor output is not adjusted. On the other hand, as a result of a hard joint, when the torque increase becomes large (when the angle increase becomes small), the control method can determine the motor output control parameter value to decrease the motor output in the next pulse, thereby reducing the torque step per pulse and ultimately improving the accuracy of the final mounting torque.

[0012] In conclusion, the present invention enables an automated procedure that provides a trade-off between the speed and accuracy of the tightening operation that better adapts to different joints.

[0013] It should be understood that one or both of the torque increase and the angle increase can be determined with respect to the previous pulse. Both of these are parameters that reflect the hardness of the joint in opposite ways. A pulse created with a given motor output will result in a larger torque increase and a smaller angle increase in a hard joint compared to a soft joint.

[0014] Furthermore, the inventor of the present invention has recognized that in an adaptive pulse strategy (i.e., a pulse strategy in which the pulse energy of a pulse is based on the torque / angle increase of the previous pulse), the energy of the last one or several pulses can sometimes vary significantly between different tightenings. Different pulse energies mean different pulse speeds, and the friction at the joint changes depending on the pulse speed. When the friction is different, the force exchange between the tool and the joint will be different, that is, the actual clamping force (N) introduced into the joint per torque (Nm) supplied by the tool is different. This can lead to a dispersion of the mounting clamping force between different joints.

[0015] In order to reduce such a dispersion of the mounting clamping force, in this aspect, upper and lower limit values are provided for the motor output control parameters, and these upper and lower limit values converge towards a preset final target window of the motor control parameter value of the last pulse. This means that different tightenings (of different joints) end with more similar pulse energies. In other words, a corridor (or envelope) is provided within which the motor control parameters (and thus the corresponding pulse energies) can vary. The corridor can be made wider at the beginning of the tightening to provide room for the adaptive algorithm to operate and vary the pulse energy, and can be made narrower towards the end of the tightening to reduce the dispersion of the energy of the last pulse between different tightenings.

[0016] According to one embodiment, the final target window can be preset based on the target torque of the tightening operation.

[0017] For example, a smaller final target window can be set for a lower target torque, and a larger final target window can be set for a higher target torque, thereby providing an improved trade-off between the accuracy of the final mounting torque and the tightening speed.

[0018] When tightening is controlled based on angle (up to a target angle), torque can be monitored as an auxiliary parameter, the target torque can be preset, and the final target window can be preset based on that.

[0019] According to one embodiment, the final target window can be preset based on the characteristics of the pulse tool (such as the maximum output of the motor, the characteristics of the hydraulic pulse unit, and the torsional behavior of the tool). For example, the minimum value of the final target window can be adjusted to provide a desired torque increase and desired precision in the final pulse at the joint where the tool is likely to be the hardest.

[0020] According to one embodiment, the width (or size) of the final target window can correspond to less than 40% of the maximum output specified for the motor, for example, less than 30% of the maximum output specified for the motor, for example, less than 20% of the maximum output specified for the motor. A narrower final target window width will result in a smaller distribution of the final mounting torque at different joints. However, if the window width is too narrow, the tightening of soft joints may be slower than desired (considering that the minimum value of the final target window should preferably be kept at a sufficiently low level to provide the desired precision in the final mounting torque of hard joints). For example, the width (or size) of the final target window can correspond to more than 5% of the maximum output specified for the motor.

[0021] According to one embodiment, the step of determining parameter values ​​indicating torque and / or angle increase may include determining the difference between a received input indicating torque and / or angle achieved in the pulse just performed and a received input indicating torque and / or angle achieved in the pulse immediately preceding the pulse just performed.

[0022] For example, parameter values ​​indicating torque and / or angle increase may be based on inputs received from a torque transducer and / or an angle encoder and / or some other means for measuring or estimating torque and / or angle in the executed pulse.

[0023] According to one embodiment, the method may further include a step of receiving an input (e.g., from a user interface) that indicates a desired trade-off between the speed and precision of the tightening operation before the tightening operation begins.

[0024] Determining the motor output control parameter value for the next pulse can further be based on the received input, which shows the desired trade-off between speed and accuracy.

[0025] For example, if the input requires a higher speed at the expense of lower precision, the motor output control parameter value for the next pulse can be determined to be higher than if the input required higher precision at the expense of lower speed.

[0026] For example, the user can select from two or more operating modes for the pulse tool, such as one precision mode, one normal mode, and one rapid mode.

[0027] This embodiment has the advantage of allowing users to adjust the trade-off between speed and accuracy to suit their specific application.

[0028] According to one embodiment, the upper and lower limits and / or the width of the final target window can be based on the received input that indicates a desired trade-off between speed and accuracy. If faster tightening is desired, a wider corridor and / or final target window can be set to allow for greater variation in pulse energy towards the end of tightening, which means faster tightening for relatively soft joints. If more precise tightening is desired, a narrower corridor and / or final target window can be set, which may suggest a stricter limit towards the end of tightening, which means less variation in the clamping force ultimately introduced (i.e., higher accuracy).

[0029] According to one embodiment, the method may further include a step of receiving an input indicating the (total) torque and / or total angle achieved in the pulse just performed (i.e., the total torque and / or total angle achieved by the tightening so far), and a step of determining the motor output control parameter value for the next pulse may be based on the received input indicating the (total) torque and / or total angle achieved in the pulse just performed. Thus, the motor output control parameter value for the next pulse may also be based on at what point in the tightening operation the next pulse is, i.e., how close the next pulse is to the target torque / target angle. At the beginning of the tightening operation, high pulse energy (motor output) is useful because it allows for rapid tightening of the initial part, while lower pulse energy (motor output) is better towards the end of the tightening operation because it improves the precision of the torque that is ultimately introduced.

[0030] According to one embodiment, the motor output control parameter value for the next pulse can be determined to be lower for larger torque increases and / or smaller angle increases, as indicated by the determined parameter value, and higher for smaller torque increases and / or larger angle increases, as indicated by the determined parameter value.

[0031] Small torque increases and large angle increases may indicate that the joint being tightened is relatively soft. This means there is room to increase motor output while maintaining the precision of the final tightening torque. Similarly, large torque increases and small angle increases may indicate that the joint being tightened is relatively stiff. This means that reducing motor output can improve the precision of the final tightening torque, even at the cost of a slightly slower tightening speed compared to not adjusting the motor output.

[0032] This embodiment can be implemented in various ways. For example, one or more thresholds can be set in advance for torque and / or angle increase. If the torque increase of the pulse just executed is greater than a predetermined first threshold, the motor output control parameter value can be determined such that the value of the next pulse is smaller than the value of the pulse just executed (for example, by a predetermined amount). Furthermore, if the torque increase of the pulse just executed is less than a preset second threshold (smaller than the first threshold), the motor output control parameter value can be determined such that the value of the next pulse is higher than the value of the pulse just executed (for example, by a predetermined amount). Similar thresholds can be set for angle increase, but the logic is reversed.

[0033] According to another embodiment, the torque / angle increase value in the previous pulse can be correlated with a specific motor output control parameter value for the next pulse in a lookup table or a predetermined function.

[0034] In this specification, the term “motor output control parameter” means a parameter that, when adjusted, causes the output power (energy) of the motor to be adjusted accordingly. It may be set as a control object of a motor control device, or converted into a control object of a motor control device. Motor output control parameters are, for example, motor output, motor current, energy output from the motor, motor torque, and motor speed (peak value of motor speed in the next pulse cycle). For example, if the motor output control parameter value is determined in terms of motor output, the determined motor output value can be used as an input to a motor control device, or it can be converted to, for example, a motor current value, which can then be used as an input to a motor control device. In this context, a motor control device means a device that controls a motor to achieve a control objective based on a received control objective (for example, part of a control device for a pulse tool).

[0035] According to one embodiment, pulses can be supplied by a hydraulic pulse unit of a pulse tool, which intermittently couples a motor to the output shaft of the pulse tool via a hydraulic coupling mechanism.

[0036] In this type of pulse tool, the motor is driven to output torque / power / energy continuously (as opposed to intermittently) during tightening, and it is the hydraulic pulse unit that generates the pulses. The motor's continuous torque / power / energy can be adjusted according to motor output control parameter values ​​that are repeatedly determined during tightening.

[0037] Alternatively, the motor itself can be driven in a pulsed (intermittent) manner to supply pulses to the output shaft of the pulse tool, in which case the motor's output power / torque / energy is zero between pulses. Therefore, the motor does not supply torque / power / energy between pulses. The intermittent torque / power / energy of the motor can be adjusted according to motor output control parameter values ​​that are repeatedly determined during tightening.

[0038] According to a second aspect, a control device is provided for controlling the motor of a pulse tool. The pulse tool is configured to supply torque in pulses during a tightening operation that tightens a screw joint. The control device is configured to perform the method according to the first aspect.

[0039] According to one embodiment, a system is provided comprising a pulse tool configured to provide pulsed torque during a tightening operation for tightening a screw joint, the pulse tool comprising a motor and a control device according to a second embodiment for controlling the motor of the pulse tool.

[0040] According to one embodiment, when the program is executed by a computer (such as a control device), a computer program is provided that includes instructions causing the computer to perform the method according to the first embodiment.

[0041] According to one embodiment, a computer-readable storage medium is provided which, when executed by a computer (such as a control device), includes instructions that cause the computer to perform the method according to the first embodiment.

[0042] It should be noted that the embodiments of the present invention relate to all possible combinations of the features described in the claims. Furthermore, it should be understood that all of the various embodiments described in the method are combinatorial with the apparatus defined according to a second aspect of the present invention.

[0043] The above and other embodiments will be described in more detail in the following exemplary and non-limiting detailed description of embodiments with reference to the attached drawings. [Brief explanation of the drawing]

[0044] [Figure 1] This shows a pulse tool equipped with a hydraulic pulse unit according to one embodiment. [Figure 2] This shows a pulse tool equipped with an intermittently driven electric motor according to one embodiment. [Figure 3] This graph shows how different parameters change during tightening according to one embodiment. [Figure 4] A method according to one embodiment is shown. [Figure 5] This graph shows how the motor output changes during five tightening cycles of five different joints according to one embodiment. [Figure 6] This is a graph showing how the motor output changes during five tightening cycles of five different joints, according to another embodiment. [Figure 7] Here is a graph showing how the motor output changes during five tightening cycles of five different joints, according to yet another embodiment. [Modes for carrying out the invention]

[0045] All figures are schematic diagrams and not necessarily to scale. In general, they show only the parts necessary to illustrate the embodiments, and other parts may be omitted. Throughout the specification, similar reference figures refer to similar elements.

[0046] A pulse tool 1 according to one embodiment will be described with reference to Figure 1. The pulse tool 1 can be configured to tighten threaded fasteners during industrial assembly. The pulse tool 1 comprises a motor 12, which may preferably be an electric motor 12. The motor 12 may comprise a rotor 14 and a stator 13. The tool 1 may further comprise an output shaft 16. The output shaft 16 may be located at the front end 10a of the housing 10 of the tool 1. The tool 1 may further comprise a hydraulic pulse unit 15 configured to intermittently couple the motor 12 to the output shaft 16 via a hydraulic coupling mechanism. For example, the pulse unit 15 may comprise an inertia drive member 18 coupled to the rotor 14 in a rotatable fixed manner. Thus, the inertia drive member 18 rotates together with the motor 12. The inertia drive member 18 may comprise a cylindrical fluid chamber 19 into which the impulse receiving portion 11 of the output shaft 16 extends. The configuration, including the cam profile and piston, is arranged to intermittently transmit rotational energy from the inertia drive member 18 to the impulse receiving portion 11. Such configurations are known to those skilled in the art and are not described further herein. An example of a hydraulic pulse unit is described in International Publication No. 9114541.

[0047] In this type of pulse tool 1, the motor 12 continuously supplies a relatively low torque, such as approximately 1 Nm. The hydraulic pulse unit 15 converts this continuous torque from the motor 12 into intermittent torque pulses on the output shaft 16, each of which can be, for example, approximately 15-55 Nm. Such a pulse tool 1 may hereafter be referred to as a hydraulic pulse tool.

[0048] Tool 1 may further include a control device 20. The control device 20 may include a processing circuit 201 and a memory 202. The control device 20 may be configured to control the motor 12.

[0049] Alternatively, the control device 20 can be located outside the tool 1 in a manner that allows it to communicate.

[0050] The tool 1 may further include a sensor 3 arranged to sense parameters indicating torque and / or angle achieved by torque pulses supplied by the output shaft 16. For example, the sensor may include an angle encoder 3 arranged to measure the angular position and velocity of the output shaft 16 (or a component in a fixed rotational relationship with respect to the output shaft 16). The angle encoder 3 can sense the angular increase achieved by the pulse just performed. It can also sense the delay in the angular velocity of the output shaft 16 due to torque transmission from the tool to the fastener. This angular velocity delay indicates the torque of the performed pulse and can therefore be used to estimate / calculate the torque achieved by the performed pulse.

[0051] As an alternative or supplement, the sensor may include a strain gauge (not shown) positioned to sense the strain on the output shaft 16 (or a component in a fixed rotational relationship with respect to the output shaft 16), which indicates the torque of the pulse being performed. For example, the sensor may include a torque transducer.

[0052] Figure 2 shows another exemplary embodiment of the pulse tool 101 of the present disclosure. In this embodiment, pulses are produced by driving an electric motor 112 in a pulsed (intermittent) manner. Pulses can be produced when the electric motor 112 accelerates in play in the gear arrangement 111 between the electric motor 112 and the output shaft 116. As a result, energy from the electric motor 112 is transferred to the output shaft 116, producing pulses on the output shaft 116. The electric motor 112 may comprise a rotor and a stator. Such a pulse tool 101 may hereafter be referred to as a direct-drive pulse tool.

[0053] For example, the gear arrangement 111 may include a play unit (not shown). Alternatively, the play unit may be arranged separately from the gear arrangement 111. The purpose of the play unit is to add play to the play present in the gear arrangement 11. The advantage of a separate play unit is that the amount of play can be selected. If a large amount of play is selected for the play unit, there is more time to control the speed of the electric motor 112 before the play in the play unit closes and the electric motor 112 couples with the output shaft 116 and imparts torque pulses to the output shaft 116.

[0054] Tool 101 may further include components similar to those of tool 1 described with reference to Figure 1 (such as a sensor 3 and a control device 20).

[0055] Next, the principles of embodiments of the present invention will be described with reference to Figures 3 and 4. Figure 3 shows how the determined motor output control parameter value M(a), the actual motor (and inertia drive member) speed (b), the pulse torque (c), and the joint mounting torque (d) change throughout the torque build-up phase (following the run-down phase) of a tightening operation performed by a pulse tool, such as one of the pulse tools described above. Figure 4 shows a method according to an embodiment.

[0056] Optionally, the control device 20 can be configured to receive an input (e.g., via a user interface) indicating a desired trade-off between the speed and accuracy of the tightening operation before the tightening operation begins (401). For example, the user can select one of the following modes: accurate mode, normal mode, or rapid mode.

[0057] First, the rundown of the tightening operation is completed. The start motor output control parameter value, which the control unit can use to control the motor accordingly, can be preset for the first one or several pulses. Optionally, this start motor output control parameter value can be the same as the rundown motor output control parameter value.

[0058] Furthermore, the control device 20 is configured to determine a parameter value indicating the torque and / or angle increase achieved by the immediately preceding pulse n (402). This can be done, for example, by calculating the difference d between the torque achieved by the just-executed pulse n and the torque achieved by the immediately preceding pulse n-1. (See graph c in FIG. 3). The angle increase can be derived directly from, for example, an angle encoder.

[0059] The control device 20 can be further configured to receive an input indicating the torque and / or total angle (i.e., the total torque and / or total angle achieved by the tightening so far) achieved by the just-executed pulse.

[0060] The control device 20 is further configured to determine a motor output control parameter value M for the next pulse n+1 (403) based on the determined parameter value indicating the torque and / or angle increase. The motor output control parameter value M is determined to be maintained between an upper limit value M max and a lower limit value M min . The upper limit value M max and the lower limit value M min can be preset to converge towards a final target window M w . The final target window M w is a predefined range / window that includes the motor output control parameter value M of the final pulse of the tightening. Thus, the algorithm managed by the control device 20 can adjust the motor output control parameter value M within the corridor defined by the upper and lower limit values M w to reach within the final target window M max , M min .

[0061] The upper and lower limit values M max , M min can be set, for example, for most (e.g., all) of the torque build-up phase of the tightening operation. For example, the upper and lower limit values Mmax M min The final target window M w It can be configured to lead to (the end of) that goal.

[0062] The method further includes controlling the motor according to a determined motor output control parameter value M to produce the next pulse n+1 (404). Thus, the motor output control parameter value M can constitute the control target when controlling the motor. The motor output control parameter value M can indicate the target energy of the next pulse n+1. The motor output control parameter can be expressed, for example, in terms of the motor output / energy / torque that the motor should output in the next pulse period, the motor current that should be input to the motor in the next pulse period, or the motor speed that the motor should output in the next pulse period, in particular the peak motor speed (see the peak in graph b of Figure 3). The rotational speed of the motor will build up to the peak speed after the pulse is executed (in both hydraulically driven pulse tools and direct-driven pulse tools). Thereafter, when torque is transmitted to the joint (via the hydraulic coupling in the case of hydraulic pulse tools), the motor speed rapidly decreases to (at least substantially) zero. The value of the peak speed determines the energy of the pulse.

[0063] The motor output control parameter value M for the next pulse n+1 can be determined to be lower for larger torque increases and / or smaller angle increases, and higher for smaller torque increases and / or larger angle increases. Thus, the algorithm executed by the control device 20 can adapt the motor output to the stiffness of the joint. As shown in Figure 3, the determined motor output control parameter value M may, for example, be increased in the first few steps and then decreased in the next steps until the end of the tightening operation. Making the steps smaller towards the end improves tightening accuracy, while making the steps larger at the beginning speeds up the tightening.

[0064] Optionally, the motor output control parameter value M for the next pulse n+1 can also be determined based on the received input, which represents the desired trade-off between speed and accuracy. When faster tightening is desired, the control device 20 can generally determine a higher motor output control parameter value compared to when more precise tightening is desired.

[0065] Furthermore, when faster tightening is desired, the upper and lower limits M are compared to when more precise tightening is desired. max M min , and / or final target window M w The range can be set more broadly.

[0066] Final target window M w This can be preset based on the target torque of the tightening operation. For example, the final target window M w Width (size) and / or final target window M w How high it can be set may depend on the target torque of the tightening operation. For higher target torques, a wider and higher final target window M w You can set a narrower and lower final target window M for lower target torques. w You can set this.

[0067] Furthermore, the width (or size) of the final target window can accommodate less than 40% of the maximum output specified for the motor, for example less than 30% of the maximum output specified for the motor, for example less than 20% of the maximum output specified for the motor, and preferably more than 5% of the maximum output specified for the motor.

[0068] Optionally, the motor output control parameter value M for the next pulse n+1 can be further determined based on the received input indicating the (total) torque and / or total angle achieved in the pulse just performed. The closer the received torque / total angle of the previous pulse is to the target torque or target angle, the lower the motor output control parameter value M can be determined for the next pulse n+1.

[0069] Step 402, which determines parameter values ​​indicating torque and / or angle increase; Step 403, which determines motor output control parameter value M; and Step 404, which controls the motor accordingly, are then repeated until the target torque and / or target angle is reached, thereby ending the tightening operation.

[0070] Figure 5 shows how the control device 20 adjusts the motor output (y-axis) as five exemplary tightening operations P1-P5 of five different joints progress (joint mounting torque is shown on the x-axis). Each circle / rhombus / square / triangle represents one pulse.

[0071] All five tightening operations P1-P5 can start with a preset motor output control parameter value, which in this embodiment corresponds to approximately 64% of the motor's maximum output.

[0072] During the tightening operation P1, the control device 20 immediately detects that the torque increase is relatively low (e.g., below a predetermined threshold) and therefore decides to increase the motor output control parameter value. As shown in the figure, the motor output control parameter value immediately reaches the maximum level, thereby the motor output is 100% of the motor's maximum output. However, as tightening progresses, the upper limit of the motor output control parameter value decreases as the motor output gradually decreases (upper limit P corresponding to the motor output). max (On the lower side) this will immediately force the motor output to (essentially) the final target window M of the motor output control parameter for a target torque of 30 Nm. w The corresponding final output window P wThe motor reaches the inside, and the tightening is complete. This can typically occur when tightening very soft joints. The generally high motor output during tightening (especially at the start of tightening) ensures that the tightening progresses faster than if the motor output remained at 64% of the initial value until the end of tightening.

[0073] On the other hand, during the tightening operation P5, the control device 20 immediately detects that the torque increase is relatively high (e.g., above a predetermined threshold) and therefore decides to reduce the motor output control parameter value. As shown in the figure, the motor output control parameter value gradually decreases until the target torque of 30 Nm is reached and tightening is completed (consequently, the motor output also decreases). However, as tightening progresses, the lower limit of the motor output control parameter will keep the motor output above the corresponding lower limit of the motor output Pmax, so the motor output will remain above the final output window P w (Final target window M for motor output control parameter values) w This can typically occur when tightening very tight joints. The generally lower motor output during tightening ensures that tightening progresses slowly and provides a more precise final mounting torque compared to when the motor output remains at 64% of the initial value until the end of tightening.

[0074] The control device 20 can operate similarly during the tightening operations P2-P4.

[0075] Figures 6 and 7 both show how the control device 20 can adjust the motor output (y-axis) as five exemplary tightening operations P1-P5 of five different joints proceed according to other embodiments (joint mounting torque is shown on the x-axis). Figure 6 shows one embodiment where the target torque is 20 Nm, and therefore the final target window is set relatively low, resulting in an acceptable final motor output P wThis is between 33% and 45% of the maximum output. On the other hand, Figure 7 shows one embodiment in which the target torque is 50 Nm, and therefore the final target window is set relatively high, and as a result the acceptable final motor output P w This is between 73% and 86% of the maximum output.

[0076] Those skilled in the art will understand that the present invention is not limited to the embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims.

[0077] In addition, by examining the drawings, disclosures, and appended claims, a person skilled in the art can understand variations of the disclosed embodiments and carry out the inventions described in the claims. In the claims, the term “comprising” does not preclude other elements or steps, and the indefinite article “a” or “an” does not preclude the plural. The mere fact that certain means are described in different dependent claims does not indicate that a combination of these means cannot be advantageously utilized. [Explanation of symbols]

[0078] 1. Pulse tool 12 motors 101 Pulse Tools 112 Motor 20 Control device 201 Processing Circuit 202 memory

Claims

1. A method (400) for controlling the motors (12, 112) of a pulse tool (1, 101), wherein the pulse tool is configured to provide torque in pulses during a tightening operation for tightening a screw joint, and the method is Step (402) of determining a parameter value (d) that indicates the torque increase and / or angle increase achieved by the pulse (n) that has just been executed, Based on the determined parameter values ​​indicating the torque increase and / or angle increase, the motor output control parameter value (M) for the next pulse (n+1) is set such that the motor output control parameter value is set to an upper limit (M) max ) and lower limit (M min The step (403) of deciding to maintain between ) and Step (404) of controlling the motor according to the determined motor output control parameter value to generate the next pulse, The steps are repeated until the target torque and / or target angle is reached, Includes, The aforementioned upper and lower limits define a predetermined final target window (M) that defines the acceptable range. w A method in which the motor output control parameter value for the last pulse of the tightening operation is set to converge toward the final target window, and the motor output control parameter value for the last pulse of the tightening operation is set to fall within the final target window.

2. The method according to claim 1, wherein the final target window is predetermined based on the target torque of the tightening operation.

3. The method according to claim 1 or 2, wherein the final target window is predetermined based on the characteristics of the pulse tool.

4. The method according to any one of claims 1 to 3, wherein the width of the final target window corresponds to less than 40% of the maximum output specified for the motor, for example less than 30% of the maximum output specified for the motor, for example less than 20% of the maximum output specified for the motor.

5. The method according to any one of claims 1 to 4, wherein the step of determining the parameter value indicating the torque increase and / or angle increase includes determining the difference (d) between a received input indicating the torque and / or angle achieved in the pulse just performed and a received input indicating the torque and / or angle achieved in the pulse (n-1) immediately preceding the pulse just performed.

6. The method according to any one of claims 1 to 5, further comprising the step (401) of receiving an input indicating a desired trade-off between the speed and precision of the tightening operation before the tightening operation begins.

7. The method according to claim 6, wherein the upper limit and the lower limit, and / or the width of the final target window are based on the received input which indicates a desired trade-off between speed and accuracy.

8. The method according to any one of claims 1 to 7, wherein the motor output control parameter value for the next pulse is determined to be lower for larger torque increases and / or smaller angle increases, as indicated by the determined parameter value, and higher for smaller torque increases and / or larger angle increases, as indicated by the determined parameter value.

9. The method according to any one of claims 1 to 8, wherein the motor output control parameter is one of motor output, motor current, motor torque, energy output from the motor, and motor speed.

10. The method according to any one of claims 1 to 9, wherein the pulse is supplied by a hydraulic pulse unit (15) of the pulse tool (1), and the hydraulic pulse unit intermittently couples the motor (12) to the output shaft (16) of the pulse tool via a hydraulic coupling mechanism.

11. The method according to any one of claims 1 to 9, wherein the motor (112) is driven in a pulse manner to supply the pulses to the output shaft (116) of the pulse tool (101), and the output of the motor is zero between the pulses.

12. A control device (20) for controlling the motor of a pulse tool, wherein the pulse tool is configured to provide pulsed torque during a tightening operation for tightening a screw joint, and the control device (20) is configured to perform the method according to any one of claims 1 to 11.

13. A pulse tool equipped with a motor is configured to provide pulsed torque during a tightening operation to tighten a screw joint, A control device according to claim 12 for controlling the motor of the pulse tool, A system equipped with these features.

14. A computer program that, when executed by a computer, includes instructions causing the computer to perform the method according to any one of claims 1 to 11.

15. A computer-readable storage medium that, when executed by a computer, includes an instruction causing the computer to perform the method according to any one of claims 1 to 11.

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