KR20180079191A - Method for controlling an electrical impulse screw-driver as a function of the instantaneous rotation frequency of its motor, and corresponding device - Google Patents

Abstract

The present invention relates to a method for controlling a discontinuous screw driver device including an electric motor connected to a terminal unit capable of rotating a rotor, wherein the motor is provided with power with a continuous power voltage pulse. According to the present invention, the method comprises a step of determining an instantaneous power voltage of the motor during each power voltage pulse, wherein the step at least comprises: a first step of measuring an instantaneous rotation frequency of the rotor in real time; a second step of determining a voltage component of the power voltage pulse which belongs to the instantaneous rotation frequency; and a third step of determining a voltage of the power voltage pulse by integrating a voltage value which depends on the instantaneous rotation frequency of the rotor.

Description

FIELD OF THE INVENTION The present invention relates to a method and an apparatus for controlling an electric impulse screwdriver as a function of the instantaneous rotational frequency of a motor of the electric impulse screw driver,

One. Field of the Invention

The field of the present invention is in the field of designing and manufacturing electrical impulse or pulse mode screwdrivers and methods of driving such screwdrivers.

2. Conventional technology

Screwdriving devices or screwdrivers are commonly used for tightening of assemblies, for example in a variety of industries, such as in automotive manufacturing.

Essentially, there are two known types of electric screwdrivers:

A continuous-tightening screw-driver device, and

Discontinuous or intermittent pulsed-mode or impulse screw-driver device.

These two types of screwdriver devices with very similar mechanical architectures are distinguished from each other by their power supply modes.

During a continuous tightening screw operation, the continuous tightening screwdriver apparatus is permanently powered with a constant or unequal voltage until a desired tightening torque is obtained.

During the impulse screwdriver tightening operation, the impulse (or pulsed mode) screwdriver apparatus is powered by successive voltage pulses until the desired tightening torque is obtained. Thus, its motor is powered discontinuously to produce a continuous torque pulse instead of a long, continuous torque increase on the screw. This reduces the reaction torque of the tool as perceived by the operator.

The present invention particularly relates to an impulse screw driver device which will now be described in more detail. Such a screwdriver device is described, for example, in Patent Document WO 2012/143532 A1 filed by the present applicant.

An electrical impulse screw driver device or screwdriver includes a transmission system between a rotating terminal unit and a motor that is capable of driving a screw, traditionally having an operating play. During the screwing phase, the motor is continuously powered by electrical pulses. In each electric pulse, the rotor of the motor accelerates and removes motion margins in the delivery system in the screwing direction. If this movement margin is removed, there is an impact on the delivery system. Thus, the rotor transmits the torque pulse to the screw associated with the terminal unit and rotates it. The rotor then rebounds with respect to the delivery system and proceeds to the maximum recoil position where the transfer motion clearance is removed in the opposite direction of the screwing direction.

During the screw tightening phase, several impact cycles are repeatedly implemented according to a given frequency until the screw tightens to the desired tightening torque.

Referring to Figure 1, which illustrates the characteristics of a pulse in terms of an electrical command, the rotational frequency of the motor, and the electromagnetic torque delivered by the screwdriver, each impact cycle includes:

Step 1: An electric pulse that powers the motor induces free acceleration of the rotor, thereby eliminating motion margins in the delivery system in the direction of screw tightening;

Step 2: Impact of the rotor in the delivery system, during which the torque pulse is transmitted to the terminal unit when the clearance is removed.

Step 3: Resetting the system through the natural rebound of the rotor induces return of the rotor to the maximum recoil position by removing motion clearance in the unscrewing direction.

Thus, the rotor moves between:

- The maximum recoil position in which the movement margin in the delivery system is maximized in the direction of screw tightening (this position prevents the output shaft and screwdriver grips from moving, The movement margin of the delivery system is removed in the screw release direction); And

- Impact position at which movement clearance is removed in the direction of screw tightening (this position is obtained when the output shaft and screwdriver grip can not move and the motor's rotor at the end of the rotation in the screw tightening direction does not move in the adjacent delivery system And the movement clearance of the delivery system is removed in the screwing direction).

During the passage from the maximum recoil position to the impact position, the rotor stores kinetic energy during acceleration to remove motion margins in the delivery system. When this movement margin is removed, the rotor delivers its kinetic energy to the screw through the delivery system during the torque pulse.

Step 1 will be examined more closely. This step tries to accumulate the energy to be partially transferred to the screw in the form of potential energy for tightening at the moment of impact.

The potential mechanical energy is given by the following simplified equation.

E _m = 1 / 2J? ²

From here,

J: Inertia of parts in motion (rotor + delivery system)

ω: Rotation frequency of the rotor of the motor along the longitudinal axis.

During the impulse screw tightening operation, the acceleration phase at each pulse must be very high, taking into account the available angular acceleration progression. It is then necessary to make best use of the accelerating capacity of the motor and its power supply.

In a continuous screwdriver device, this need for high acceleration does not exist.

The electrical impulse screwdriver apparatus is characterized in that it comprises an " open loop " during the rotor acceleration phase which depends on a set value of the power supply voltage in each impact cycle based on a predetermined " template & open loop " mode. Such a template enables adjustment of the supply voltage during the acceleration phase. However, this does not take into account its effect on the actual (or momentary) rotational frequency of the motor. Such a template consists of a correspondence table associating a plurality of pairs of instantaneous values with a supply voltage value.

This template is determined in the laboratory for a typical screwdriver device and a given screwdriver operation. It is then used in production to register with a controller that performs driving of the screwdriver to drive the motor's power in time to perform predetermined screwdriver operation.

Figure 2 shows the following:

- an example of such a template (voltage template) representing the power supply voltage of the motor as a function of time,

The transition of the current consumed by the motor as a function of time, and

- Fluctuation of motor's rotational frequency during electrical power pulse.

In Figure 2, it can be seen that:

- the supply voltage is constant at every moment of the electrical power pulse;

- there is a current spike when the motor is started and there is a gradual decrease in current during the motor's acceleration;

- a decrease in the slope of the rotational frequency during the electric pulse, in other words, a reduction in the acceleration (a slightly curved rotational frequency curve with a directional coefficient over time).

The causes of this acceleration decrease during the electric pulse are as follows:

Assemblies, referred to as screwdriver systems, formed by the screwdriver device and its controller are limited by design in its ability to deliver a maximum current, for example, 75 amperes. Exceeding this maximum current causes blockage, which requires action by a maintenance technician to block the block, in order to protect the screwdriver.

Thus, the amplitude of the power source at low rotational frequency (at start-up) is proposed by its maximum permissible current in accordance with Ohm's law U _max = R · I _max , where U _max is the maximum allowable power supply voltage and I _max is the maximum Is the allowable current, and R is the resistance of the system formed by the screwdriver and its controller.

The setpoint voltage template is therefore limited by its maximum allowable amplitude.

Now, as the rotational frequency of the rotor increases, the motor generates a voltage called a counter-electromotive force or back electromotive force whose value is proportional to the rotational frequency, and this counter electromotive force is obtained from the power supply voltage of the motor. Thus, the payload voltage tends to decrease during the voltage pulse. This results in a reduction in the current consumed by the motor, and thus a reduction in the instantaneous electromagnetic torque, as observed in the graph.

This limits the rotational frequency that the motor can achieve at the end of the electric pulse and thus limits the kinetic energy that the controller can provide to the screwdriver during its pulse as the rotational frequency increases.

Now, the limitation of this kinetic energy that can be transmitted to the screw limits the tightening capacity of the screwdriver, which is the amount of movement margin in the gear reduction system or, generally, in the kinematic chain between the motor and the screw By increasing the angular acceleration progress which is itself limited by the motion margin of the motor.

A voltage of a predetermined set value is applied during the electric power supply pulse,

- limit of maximum current;

- reduction in payload voltage resulting from an increase in counter-electromotive force during an electric pulse

A voltage template that is no longer constant and variable in time has been developed to overcome the disadvantages of the prior art. Such a template is shown in Fig.

As can be seen, the voltage template has a low initial value which then increases with time.

With this type of template, the following is noted:

- the initial low value of the supply voltage results in a smaller current spike at start-up: thus preventing the controller from exceeding the maximum allowable current and starting the device;

The gradual increase in the power supply voltage after the start phase, to a large extent, makes it possible to compensate for the increase in counter-electromotive force at the rotational frequency and obtain a more constant current during power supply of the motor.

Thus, the use of a voltage template with a variable power supply has the advantage of providing a more constant electromagnetic torque and the ability to obtain higher electromagnetic torques for longer periods without the risk of shutdown of any controller, And has the effect of generating a stable motor acceleration.

According to another aspect, and depending on the elasticity of the assembly and the target level of torque, it may be useful to adjust the level of kinetic energy before impact prior to the end of the electric pulse. For this purpose, the template is set up for applications that require the greatest number of pulses, and the application of modulating coefficients (referred to as " pulse amplitudes ") requiring lower screw driving power , I.e. for assemblies that have low resilience and require low screw driving torque. For example, if the usage requires 60% of the power of the base template, a homothetic transformation at 60% of the base template can be achieved.

Thus, the equation used to determine the voltage applied at a given instant t is:

U (t) = TabTemplate [t] x PulseAmplitude

From here,

U (t): voltage applied at instant t

TabTemplate [t]: a table that contains all the points of the desired template and is indexed as a function of the instant (t)

PulseAmplitude: Amplitude factor with a range from 0 to 1

A template at about 60% of the base template shown in FIG. 3 is shown in FIG. In this figure, the application of resemblance transformation does not allow the current consumed by the motor during the pulse to be maintained at a perceptible level. Thus, the resembling transformation can not be used to obtain a constant motor torque and a stable acceleration that is not reduced when the rotational frequency of the motor increases.

Therefore, in addition to the case of the basic template, the template set in consideration of the change in the power supply voltage of the motor in time does not prevent a reduction in the voltage that is truly required for the motor, and therefore, the reduction in the current applied to the motor, Lt; RTI ID = 0.0 > and / or < / RTI > decrease in rotor acceleration.

Thus, a simple change in the setpoint of the supply voltage as a function of time is not sufficient because it only works for given (if used to set the base template), and the base template is not sufficient It does not cover all possible use cases.

FIG. 5 shows the relationship between the current consumed by the motor during the implementation of the template of FIG. 3 and the time of the rotational frequency of the rotor in the situation where the rotor of the motor is cut off before the end of the pulse (the rotational frequency drops at the end of the power supply voltage pulse) As a function. This interruption of the rotor of the motor may occur when the available clearance in the delivery system is permanently reabsorbed for free acceleration of the rotor before the power pulse of the motor is completed.

In this case, a large increase in the current or intensity consumed by the motor is seen when the motor's rotation frequency drops due to the interruption experienced by the motor. Thus, the useful voltage of the motor is large when compared to its rotational frequency, and the current therefore increases beyond the allowable limit by the system. This can lead to defects that activate the security system to shut down the controller and shut down the screwdriving operation due to exceeding the maximum current allowed by the system, which is not acceptable in an industrial screwdrive drive environment Can not be.

Thus, the use of a power supply voltage template as a function of time in accordance with the prior art does not make it possible to drive one and the same kind of screwdriving device in different usage situations, and can occur during screwdriving operations without causing interruption of the controller (Such as shutting off the rotor, moving along a hard point during assembly, etc.), this is because the blocking of the controller implies measures by the maintenance technician and thus takes time, Levels are not allowed.

Therefore, the driving of the electric impulse screw driving device can be further improved.

3. Object of the Invention

The present invention is particularly directed to providing an efficient solution to at least some of these different problems.

In particular, in accordance with at least one embodiment, it is an object of the present invention to optimize the operation of a motor of a discontinuous or intermittent electrical impulse screwdriver device.

In particular, it is an object of the present invention, in accordance with at least one embodiment, to enable a motor to produce a substantially constant electromagnetic torque over each of the electrical supply voltage pulses.

It is another object of the present invention, in accordance with at least one embodiment, to enable a motor to produce high electromagnetic torque without causing any risk exceeding the maximum current allowable by the screwdriver system.

The present invention also provides, in at least one embodiment, any excess current in the case of continuous electrical power supply, without causing interruption of the operation of the screwdriver system, and in particular, even if the margin of motion in the kinematic chain is eliminated. Seeking the purpose of coping with the operation abnormality without generating it.

In at least one embodiment, it is another object of the present invention to tailor the base template to other usage situations by the principle of resemblance transformation without deterioration at the performance level.

4. Presenting the present invention

For this purpose, the present invention proposes a method of controlling a discrete screwdriver apparatus comprising an electric motor to which a rotor is connected to a rotatable terminal unit, the motor being powered by a continuous supply voltage pulse.

According to the present invention,

A first step for real-time measurement of the instantaneous rotational frequency of the rotor, and

A second step characterized by determining a voltage component of the power supply voltage pulse that is dependent on the instantaneous rotational frequency,

Integrating the voltage value depending on the instantaneous rotational frequency of the rotor to determine the voltage of the power supply voltage pulse in real time;

And determining an instantaneous power supply voltage of the motor during each of the power supply voltage pulses.

Thus, in accordance with this aspect, the present invention relates to determining the voltage of each supply voltage pulse of a motor of an intermittent or discontinuous tightening screwdriver device by including a component whose value is dependent on the rotational frequency of the rotor of the motor Feature.

Considering the rotational frequency of the rotor to determine the voltage of each supply voltage pulse increases with the rotational frequency of the motor and allows compensation of the counter electromotive force subtracted from the voltage consumed by the motor to produce an electromagnetic torque.

Thus, the present invention makes it possible to acquire a more constant current during the power supply time of the motor, thereby avoiding the electromagnetic torque and thereby the reduction of the rotor's acceleration.

The present invention also makes it possible to produce a high electromagnetic torque without any risk of exceeding the maximum current allowed by the screwdriver system by obtaining a variation in the voltage of the supply voltage pulse as a function of the motor's rotational frequency . In fact, the voltage of the power supply voltage pulse may be low enough at start up to not exceed the maximum value of the allowable current by the system, and then, to compensate for the loss of electromagnetic torque due to the increase in the rotational frequency, And thus ensures that a high level of electromagnetic torque is obtained.

Thus, the present invention optimizes the operation of the motor of an intermittent or discontinuous electrical impulse screw driver device.

According to one possible advantageous feature, said component is selected as a function of said instantaneous rotational frequency from a predetermined set of voltage values.

In this case, different types of screwdriver devices implemented to perform different types of screwdriver operation, different rotational frequencies of the rotor, loss of electromagnetic torque due to an increase in the rotational frequency of the rotor, A lab attempt will be made to determine the value of the component that enables compensation for driver operation or for those that require the greatest amount of energy. This data can be recorded in the screwdriver device and selected during its type and parameterization of the screwdriver device as a function of the type of screwdriver operation to be achieved before it is put into production.

According to another possible advantageous feature, said component is determined as a product of said instantaneous rotation frequency and a predetermined coefficient.

In this case, instead of being selected, the value of the component will be calculated in real time.

According to one possible advantageous characteristic, each voltage of the power supply voltage pulses,

A first term corresponding to a predetermined theoretical constant power supply voltage multiplied by a pulse amplitude coefficient; and

- a second term corresponding to said component dependent on the instantaneous rotational frequency of said rotor

. ≪ / RTI >

The voltage of each power supply voltage pulse corresponds to the sum of the theoretical constant power supply voltage required to obtain the predetermined rotation frequency when the motor is started and the dependent component of the rotation frequency. This component makes it possible to compensate for the increase in voltage generated by the counter electromotive force at the rotational frequency of the rotor and to obtain a more constant current and corresponding electromagnetic torque while the motor is powered.

The theoretical voltage value of claim 1 will be multiplied by a pulse amplitude coefficient that preferably varies from 0 to 1.

For a given type of screw tightening device, it will be possible in the laboratory and for a given type of screwing device to determine the intrinsic value of the theoretical constant supply voltage for the type of screw driver operation that requires maximum power will be. To fit this theoretical value to the operation requiring less power, the theoretical value in the strictest case will be multiplied by the amplitude factor. Thus, if the screw driver operation to be performed requires only 80% of the power required for screw driver operation under the most stringent conditions, the amplitude factor would be 0.8.

 The fact that this amplitude coefficient applies only to the first term, which is constant and does not apply to the second term, which varies as a function of the rotational frequency of the rotor, means that there is a constant intensity consumed by the motor, regardless of the type of screwdriver operation, Ensuring that the electromagnetic torque is maintained.

Advantageously, said predetermined theoretical constant supply voltage is the product of the predetermined current value and the electrical resistance of said screwdriver device.

Preferably, the second term is a product of the instantaneous rotational frequency of the rotor and the counter electromotive force coefficient of the motor.

According to one possible advantageous feature, the second term considers data stored in the form of a correspondence table associating a plurality of pairs of power supply voltage values and the rotational frequency value of the rotor.

Thus, the implementation of the method is faster because it uses the recorded data instead of performing the calculations to determine the second term.

According to one possible advantageous characteristic, the method according to the invention comprises the steps of detecting an operation error and correcting the voltage of the power supply voltage pulse of the motor in accordance with detection of the operation or the like.

Anomalies may occur during screw tightening or screw loosening operations: especially when the clearance in the delivery system is corrected before the end of the motor's power supply voltage pulse, the rotor is blocked. This causes the maximum value of the allowable intensity to be exceeded by the screwdriver device causing the interruption of the screwdriver device.

To overcome this problem, the technique of the present invention proposes the detection of an anomalous occurrence, and hence the correction of the power impulse voltage of the motor to keep the intensity below the maximum allowable value by the screwdriver device. Thus, this technique avoids the need to shut down the motor and the production line, and the need for the maintenance technician to take action to restart it.

In this case, the step of detecting the operation abnormality preferably includes:

- measuring the electrical power consumed by the motor;

Comparing the measured value of the electrical strength consumed by the motor with a predetermined threshold value;

- reducing the voltage of the power supply voltage impulse of the motor when the measured value of the electric power consumed by the motor is above the threshold value

.

According to a preferred variant, reducing the voltage of the supply voltage pulse of the motor is characterized by decreasing the first term of the voltage of the supply voltage pulse.

This effectively prevents the maximum value of allowable intensity from being exceeded by the screwdriver device.

According to another preferred variant, the step of reducing the voltage of the power supply voltage pulse of the motor is characterized by decreasing the product of the first term and the amplitude coefficient and the sum of the second term.

This more quickly prevents the maximum value of allowable intensity from being exceeded by the screwdriver device.

The present invention also relates to an electric motor in which a rotor is connected to a terminal unit which can be driven to rotate, and a discontinuous screw driving system including power supply means of the motor by continuous power supply voltage pulses.

In this system,

Means for real-time measurement of the instantaneous rotational frequency of the rotor; And

Means for determining a voltage component of the power supply voltage pulse dependent on the instantaneous rotational frequency;

Means for integrating the voltage value dependent on the instantaneous rotational frequency of the rotor to determine the voltage of the power supply voltage pulse in real time;

And means for determining an instantaneous supply voltage of the motor during each of the supply voltage pulses

.

According to one possible advantageous feature, the means for real-time determining the voltage of the supply voltage pulse comprises:

A first term corresponding to a predetermined theoretical constant power supply voltage multiplied by a pulse amplitude coefficient; and

- a second term corresponding to said component dependent on the instantaneous rotational frequency of said rotor

And a means for calculating the sum of the two.

According to one possible advantageous characteristic, the system according to the invention comprises means for detecting an operation error and means for correcting the voltage of the power supply voltage pulse of the motor in accordance with detection of the operation or the like.

In this case, the means for detecting the operation abnormality preferably includes:

Means for measuring the electrical strength consumed by the motor;

Means for comparing the measured value of the electrical strength consumed by the motor with a predetermined threshold value;

Means for decreasing the voltage of the power supply voltage impulse of the motor when the measured value of the electric power consumed by the motor is greater than or equal to the threshold value

.

According to one possible advantageous feature, the means for reducing the voltage of the power supply voltage impulse of the motor reduces the first term of the power supply voltage pulse.

According to another possible advantageous feature, the means for reducing the voltage of the power supply voltage impulse of the motor reduces the product of the first term and the amplitude coefficient and the sum of the second term.

The present invention also relates to a computer program product, when executed on a computer, comprising program code instructions for implementing a method according to any of the preceding variations.

The present invention also relates to a computer readable and non-volatile storage medium for storing a computer program product according to the variant as described above.

5. List of drawings
Other features and advantages of the present invention will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, in which:
1 shows the shape of the pulse relating to the command, torque and rotational frequency of an intermittent or discontinuous tightening screwdriver;
Figure 2 shows the shape of a time-related template of constant voltage according to the prior art;
Figures 3, 4 and 5 illustrate the shape of a time-related template of non-constant voltage according to the prior art;
Figures 6 and 7 illustrate an example screwdriver and controller of a screwdriver system according to the present invention;
Figures 8 and 9 show two terms of the template formed in accordance with the invention shown in Figure 10;
11 schematically shows the regulation principle of the method according to the invention, shown in the form of a flow chart in Fig. 12; Fig.
Figures 13 to 16 show different shapes of the power supply voltage pulses according to the invention;
17 shows a flowchart of the safety system in the power supply according to the present invention in the case of abnormal operation detection, Figs. 18 and 19 show the principle and shape of the power supply voltage pulse in the case of simple security, And 21 show the principle and shape of the power supply voltage pulse in the case of enhanced security.

6. certain In the embodiments  Explanation

6.1. Screw driver device

The present invention is applied to a screw driver device or an electric screw driver called an intermittent or discrete screw driver tightening device.

6, this kind of screwdriver 1 conventionally includes a casing 10 which accommodates an electric motor 11 provided with a stator 110 and a rotor 111. As shown in Fig. The rotor 111 is connected to a terminal unit 13 which can be rotationally driven using a delivery system 12 having a motion motion margin and cooperates with the screw to correct for screwing or unscrewing during assembly operations.

As described in the context of the prior art, the motor of such a screwdriver apparatus is powered by a continuous supply voltage pulse.

The example described here consists of a screwdriver 1, which itself is connected to the controller 2 connected to the company's electrical power network by a cable. This controller enables control of the operation of the screwdriver and its electrical power source.

In one variation, the energy source may be a battery fixed to the screwdriver, in which case the controller is integrated into a screwdriver that can be miniaturized and autonomous.

The screw driver,

A power cable (21) for the motor;

- a transmit / receive module (22) that enables the screwdriver and controller to communicate by cable or wirelessly and to communicate with other devices, such as a computer network,

To the controller. Thus, such a screwdriver may receive command signals from the controller, and the controller may receive signals from different sensors incorporated in the screwdriver.

7, the controller 2 includes a random access memory (RAM) 23, for example a program code instruction for a process and for executing a driving method according to the present invention , And the program is stored in a read-only memory 25 (ROM). Traditionally, the controller comprises in particular an input / output interface 26 for enabling this program and, optionally, an information input means such as a screen 27 and a keypad or mouse 28. This includes a power source 29 for the motor 11 and a sensor 30 for sensing the current consumed by the motor 11, which is traditionally located in the phase of the motor.

Initially, the code instructions of the computer program are loaded into the random access memory 23, for example, and then executed by the processor of the processing unit 24. [ The random access memory 23 in particular comprises suitable equations for calculating the different variables determined during the application of the method. The processor then drives the screwdriver device accordingly.

Figure 7 illustrates one particular way (among any of the different embodiments, or a combination of these embodiments) of the various possible ways for the controller to perform the steps of the driving method according to the present invention. Indeed, these steps may be performed on a reprogrammable computer machine (PC computer, DSP processor or microcontroller) or a dedicated computing machine (e.g., a logic gate set such as an FPGA, an ASIC or any other Hardware modules). ≪ / RTI >

Once the controller is fabricated with a reprogrammable computing machine, the corresponding program (i. E., The sequence of instructions) may be stored in a removable storage medium (e.g., floppy disk, CD-ROM, DVD-ROM) And the storage medium is partially or entirely readable by a computer or a processor.

The system typically includes means for real-time measurement of the instantaneous rotational frequency of the rotor including the angle sensor 14 integrated into the screwdriver device on the shaft of the rotor. Such an angle sensor includes, for example, a Hall effect sensor set of magnets that can be fixedly attached to a rotating rotor as it rotates, in a manner known per se. Depending on the position of the rotor, the assembly constituted by the magnet and Hall effect sensor produces an electrical signal, the level of which represents the position of the rotor. The measuring means for measuring the rotational frequency of the rotor obtains the position of the rotor with respect to time to determine its rotational frequency.

The controller and the different sensors of the screwdriver constitute different means for implementing the steps of the drive method according to the invention, as will be seen in more detail in the following description of the drive method according to the invention.

6.2. General principle

The present invention includes a pulse-type instantaneous power supply voltage value of a motor by including a component whose value depends on the instantaneous rotational frequency of the rotor of the motor during the acceleration phase of the rotor of the discontinuous tightening screwdriver apparatus, And a value of < / RTI >

In this embodiment, the equation for connecting the voltage, the intensity, and the rotational frequency is as follows:

U = R · I + ψ · ω

From here,

U: Voltage applied to the motor (in volts)

I: Current applied to the motor (amperes)

ω: Rotational frequency of motor (rpm)

R: Electrical resistance of screw driver devices (control electronics, cables and motors)

ψ: motor back-electromotive force voltage coefficient

In a permanent magnet synchronous motor, the torque transmitted by the motor is proportional to the intensity.

Thus, a given level torque has a corresponding level of intensity I. At the start of motor acceleration, ie at zero rotation frequency, the power supply voltage of the motor must be equal to R · I for the intensity set at this level. In order to maximize the tightening capacity of the system, the level of intensity can be the maximum level of strength that this system can tolerate.

When the rotation frequency increases, the counter electromotive force increases. In order to preserve the electromagnetic torque and thus the intensity consumed by the motor at the maximum level Imax, the power supply voltage of the motor must be increased by the value of the voltage of the counter electromotive force.

Thus, considering the rotational frequency of the rotor in order to determine the value of the instantaneous power supply voltage of the motor makes it possible to compensate for the counter electromotive force which increases with the rotational frequency of the motor, so that a constant electromagnetic torque and a constant Thereby making it possible to obtain current.

The set value of the voltage of each power supply voltage pulse is,

A first term corresponding to a predetermined theoretical constant power supply voltage multiplied by a pulse amplitude coefficient; and

- the second term corresponding to the component dependent on the rotational frequency

. ≪ / RTI >

In this embodiment,

The first term of the voltage is a constant value that determines the level of intensity consumed by the motor at zero rotation frequency. This can be expressed in the form of PulseAmplitude 占 offset,

- PulseAmplitude: Amplitude factor

- Offset: 0 Voltage whose intensity consumed by the motor at the rotational frequency is the maximum level of intensity allowed for the screwdriver system

to be.

- The second term compensates for the effect of the back electromotive force and makes it possible to maintain the intensity at a constant level during the acceleration phase of the rotor.

Two variants can be envisaged in production:

The first variant is characterized by real-time calculation of the second term based on a real-time measurement of the rotational frequency of the rotor,

- The second variant is characterized by using a table of correspondences pre-recorded in a memory of the controller which associates a plurality of pairs each including a supply voltage value (i.e. added to the supply voltage) and a rotational frequency value of the rotor .

According to a first variant, the value U (t) of the supply voltage pulse at instant t is:

U (t) = PulseAmplitude 占 Offset + ψ · ω (t)

ω (t) is the instantaneous rotational frequency of the motor at instant t.

ψ is the motor's back-EMF voltage coefficient. These parameters, which are known to those of ordinary skill in the art, can be determined by calculation or can be measured experimentally in a laboratory.

According to a second variant, the value U (t) of the power supply voltage pulse at instant t is:

U (t) = PulseAmplitude 占 Offset + TabTemplate [Speed (t)]

From here,

Speed (t): Rotation frequency of motor at instant t

TabTemplate [Speed (t)]: A table containing the set of desired power supply voltage points indexed as a function of the different rotational frequencies of the rotor (the values in this table may be the result of a laboratory experiment)

Offset: Maximum value of the voltage offset suitable for the screwdriver system.

PulseAmplitude: Coefficient in the range of 0 to 1

to be.

11, the driving of the power source of the motor is characterized by correcting the offset by addition of the voltage component as a function of the actual rotational frequency (speed) of the motor M based on the predetermined template , This template corresponds to the table corresponding to the product ψ · ω (t) in the first case and the result of the product ψ · ω (t) for different values of ω (t) in the second case.

There are different types of screwdriver systems, each of which is particularly characterized by its screwdriver delivery system, its dimensions, its efficiency, its motor drive and the like.

Each type of screwdriver system can be applied to production to perform different screwdriver strategies. Although this is not possible, it is difficult to parameterize each kind of screwdriver system for all screw fastening operations that are easy to use.

Thus, each kind of screwdriver system is parameterized according to the screwing operation under the most stringent conditions which are easy to implement, i.e., the screwing operation which requires the greatest amount of energy.

6.3. Spare during the manufacture of the screwdriver system Parameterization

Each kind of screwdriver device must be parameterized before being used in production.

The parameterization is characterized in that for each new kind of screwdriver system implemented for its application under the most stringent conditions, it determines the parameters suitable for its subsequent use in production to drive the motors of each system of the same kind have.

In conjunction with the first variant, these parameters are:

- an offset equal to the product of the electrical resistance of the screwdriver system and the maximum permissible strength permitted by the system to be blocked;

- ψ.

In conjunction with the second variant, these parameters can be used for a record of a table containing the value of the corresponding additional voltage in order to compensate for the loss of efficiency due to an increase in the rotational frequency of the rotor, , And this additional voltage is the product [psi] [omega] [omega].

Offset, psi and TabTemplate [Speed (t)] can be determined for all at once and these parameters are suitable for the type of screwdriver system and remain unchanged for the lifetime of the screwdriver.

The first term of the power supply voltage pulse can be shown by the curve of Fig. 8 showing, for example, the offset voltage as a function of the rotational frequency of the rotor, which is a constant Do.

The second term of the power supply voltage pulse can be shown by the curve of Fig. 9, which shows the transition of the additional voltage, for example, to the offset voltage as a function of the rotational frequency of the rotor.

The value of each power supply voltage pulse transmitted to the motor corresponds to the sum of the first and second terms. The curve of Fig. 10 shows an example of the transition of this power supply voltage as a function of the rotation frequency of the motor. An example of this curve corresponds to the sum of the curves of Figs.

6.4. Production preparation

The parameters (Offset and TabTemplate [Speed (t)]) required to drive the motor of the screwdriver system are recorded in memory during its manufacture (see § 6.3).

When a screwdriver system is used in production, it can be confronted with assemblies of varying thicknesses or with assemblies that require different levels of torque.

It is therefore necessary to reduce the tightening power of this screwdriver, especially for low tightening torque values. To enable this, the parameter " PulseAmplitude " is selected as a function of the respective application or assembly to be manufactured. For each particular application, it corresponds to a percentage of the power in the most stringent state required by this particular application and determines the level of kinetic energy that accumulates in the rotor of the motor before impact.

When the screwdriver device is implemented to perform different types of screw tightening operations, parameters are defined that define the screw tightening strategy to be applied to each application. These parameters include in particular the level of torque to be obtained, the pre-thread tightening speed and the amplitude coefficient PulseAmplitude. The coefficient PulseAmplitude is determined experimentally by the department that defines the screw tightening strategy.

These parameters are written to the tool's memory and used as a function of the application they are facing.

6.5. How to drive in production

6.5.1. Typical case: No abnormal behavior

The driving method according to the present invention is implemented during the performance of the screw tightening operation.

Typically, a screw tightening operation occurs after activation by an operator, for example, in accordance with a discrete screw tightening strategy programmed into the controller, during which the motor is powered by an electrical power supply voltage pulse.

However, during the performance of the screw driver operation, in accordance with the present invention, a specific drive is implemented to determine the value of each voltage power pulse of the motor. This method is repeatedly implemented in each pulse until the end of the screw tightening operation.

Determining the value of each pulse of the supply voltage pulse assumes the implementation of step 120 for real-time measurement of the instantaneous rotational frequency omega (t) of the motor. This is typically done by obtaining a derivative with respect to time for a signal coming from the position sensor of the rotor.

Then, one component of the value of the power supply voltage pulse that depends on the instantaneous rotational frequency is determined during step 121. [

Next, the value U (t) of the power supply voltage pulse is determined by integrating the voltage value dependent on the rotational frequency during step 122.

In the case of the first variant, the second term of the value of the power supply voltage pulse is calculated during step 1210 from the measured value of the rotational frequency of the rotor in accordance with the equation ψ · ω (t). The value of each supply voltage pulse U (t) is then calculated by the controller during step 122 according to the following equation:

U (t) = PulseAmplitude 占 Offset + ψ · ω (t)

The values of PulseAmplitude, Offset and ψ are in the system memory. Then a voltage command is sent to the motor.

In the case of the second variant, the second term is obtained during step 1211 by extracting the value of the second term corresponding to the current rotation frequency from the table TabTemplate [Speed (t)] recorded in the memory of the controller. The value of each supply voltage pulse U (t) is then calculated by the controller during step 122 according to the following equation:

U (t) = PulseAmplitude 占 Offset + TabTemplate [Speed (t)]

Figure 13 shows that in the present example of the rotational frequency of the rotor, the power supply voltage pulse command to the motor and the current consumed by the motor in the case of the execution of the screw driver operation performed under the most stringent condition with an amplitude factor PulseAmplitude of 1, Lt; RTI ID = 0.0 > time. ≪ / RTI >

You can see that:

- the variation of the speed during the power supply voltage pulse is perfectly straight (constant acceleration of the motor) and does not curve as in the prior art;

- the current consumed by the motor is stable;

This is achieved in accordance with the invention by changing the set point of the voltage as a function of the rotational frequency of the rotor.

Figure 14 shows that for applications requiring only 30% of the power required for the application under the most stringent conditions with an amplitude coefficient of PulseAmplitude of 0.3, it is possible to reduce the rotational frequency of the rotor, the power supply voltage pulse command to the motor, Lt; RTI ID = 0.0 > 5 ms. ≪ / RTI >

It can be seen that the transition of the velocity is perfectly straight and constant and the current is stable, as in the normal case occurring under the most severe conditions. The correction of the offset only affects the final speed obtained at the end of the supply voltage pulse, but does not impair the linearity of the speed or current consumption variation of the motor.

6.5.2. Management of overheads

i. Slightly  More than

15 shows the duration of the spinning frequency of the rotor, the power supply voltage pulse command to the motor, and the current consumed by the motor in this example of 5 ms in the case of a screw tightening operation performed under the most stringent conditions with an amplitude coefficient PulseAmplitude of 1 Lt; / RTI > during the power supply voltage pulse.

Here, the rotation frequency is not completely linear (linear or constant), but is reversed. This disturbance results from a slight malfunction such as, for example, minor fluctuations in the strength of the assembly during the tightening (friction). However, the system causes the supply voltage to vary as a function of the rotational frequency of the rotor to maintain a substantially constant current value.

Thus, in some cases, the system corrects the power supply voltage to preserve the allowable current.

In some use cases, the motor can be significantly slowed or blocked (such as when passing through the design point, screwing excessively, etc.) during screw tightening or screw loosening operations. This is a result of the fact that the value has caused a sharp rise in current which may exceed the maximum allowable value by the system.

In this case, the duration of the spinning frequency of the rotor, the power-supply voltage pulse command to the motor, and the current consumed by the motor in this example of 5 ms in the case of performing the screw tightening operation under the strictest condition with an amplitude coefficient PulseAmplitude of 1 Lt; RTI ID = 0.0 > 16 < / RTI >

Here, you will notice that the motor is "slightly" interrupted before the end of the supply voltage pulse (approximately 0.0065 s of rotational frequency drop).

This kind of interruption occurs when the margin of motion in the delivery system is absorbed before the end of the electrical supply voltage pulse. This may be the result of insufficient rebound of the motor not returning to the maximum recoil position or not acquiring acceleration progression for the rotor corresponding to the overall value of the angular motion margin of the delivery system.

However, during a drop at the rotational frequency due to the interruption of the rotor, the system adjusts the supply voltage to prevent a sharp rise in current.

However, the method has limitations because the system is sized to cover small variations in the rotational frequency of the motor in the case of optimum use.

However, the basic system can not prevent the interruption of the motor much earlier in the acceleration phase of the power supply voltage pulse. There are also other external disturbances that can hardly be modeled, such as problems caused by temperature and internal resistance of the system that can vary with the aging of the equipment or the stability of the voltage of the power grid supplying the system.

For example, in order to manage the occurrence of the more serious anomalies when the rebound of the rotor does not occur correctly and when angular advances available for motor acceleration are significantly reduced, the method according to the present invention provides a security system .

ii. more  A serious error

Referring to FIG. 17, this security includes a step 170 for detecting an operation abnormality in real time, and a step 171 for correcting the value of the power supply voltage pulse of the motor in accordance with the detection of the operation abnormality.

More specifically, the step 170 of detecting an operation anomaly and the step 171 of correcting the value of the power supply voltage pulse,

- step 1701 for real-time measurement of the electric power consumed by the motor;

- comparing the measured value of the electrical intensity consumed by the motor with a predetermined threshold value 1702; This value will preferably be the maximum value of the intensity acceptable by the system, for example, 75 amperes;

- step 1710 for reducing the power supply voltage of the motor when the measured value of the intensity produced by the motor is above a threshold value.

Several types of security can be implemented:

- simple security;

- reinforced security.

ii. One. simple  security

In conjunction with so-called simple security, step 1710 for reducing the power supply voltage of the motor is characterized by the first term of the power supply voltage, i.e. the reduction of the offset in this case (step 17101).

Thus, as shown in Fig. 18, this simple security is characterized in that the offset is strictly limited, whatever this may cause, only when an excessively high current is detected.

Fig. 19 shows the duration of the spinning frequency of the rotor, the power supply voltage pulse command and the current consumed by the motor in this example of 5 ms when the screw tightening operation of the rotor is performed under the most severe condition with the amplitude coefficient PulseAmplitude of 1 Of the power supply voltage pulse. Here, it can be seen that the motor is shut off for the "long time" before the end of the power supply voltage pulse (the rotational frequency drop to approximately 0.0055 s).

In this case, it is inevitable that the current will ultimately increase. Regulation of the supply voltage will not be efficient enough to prevent this phenomenon. However, the current-based security can be activated at the threshold to strictly limit the setpoint voltage.

Then, the performance of the pulse will be very badly damaged, but will prevent current faults and shutdown of the system.

Simple security in the current allows the offset to be limited, for example by automatically reducing the coefficient PulseAmplitude applied to the supply voltage pulse by applying an experimentally determined adjustment factor (e.g., 0.5). This makes it possible to terminate the screw tightening operation without exceeding the maximum allowable current value by the system. This occurs, for example, when the rotor is disconnected and / or when an improper power cable is used.

ii. 2. reinforce  security

If the implementation of simple security is not sufficient, enhanced security can be implemented. In conjunction with this enhanced security, step 1710 for reducing the power supply voltage of the motor is characterized by multiplying the first term by the amplitude coefficient and decreasing the sum of the second term (step 17102).

Thus, as shown in FIG. 20, this enhanced security allows the sum of the additional voltage and offset, which vary as a function of the rotational frequency when an excessively high current is detected, to be adjusted, for example, by experimentally determined adjustment factors , 0.5) is automatically applied to this sum.

Fig. 21 is a graph showing a power supply voltage having a duration of 5 ms in the present example of the rotational frequency of the rotor, the power supply voltage pulse command, and the current consumed by the motor when the screw tightening operation is performed under the most severe condition with the amplitude coefficient PulseAmplitude = Represents the variation during the pulse.

Here, it can be seen that the application of the reinforced security reduces the power supply voltage more rapidly.

6.6 Variation example

In one variation, the present invention is not only a function of the motor's back electromotive force voltage coefficient, but also a function of the power supply voltage pulse as a function of other parameters of the system such as phase shift, speed, efficiency, internal resistance, inertia, Can be improved by determining the second term of the voltage.

Claims (20)

A method of controlling a discontinuous screwdriver apparatus comprising an electric motor to which a rotor is connected to a terminal unit that can be rotationally driven,
The motor is powered by a continuous supply voltage pulse,
The method comprises:
A first step for real-time measurement of the instantaneous rotational frequency of the rotor, and
A second step characterized by determining a voltage component of the power supply voltage pulse that is dependent on the instantaneous rotational frequency,
Integrating the voltage value depending on the instantaneous rotational frequency of the rotor to determine the voltage of the power supply voltage pulse in real time;
Determining an instantaneous supply voltage of the motor during each of the supply voltage pulses,
≪ / RTI >
A method of controlling a discrete screwdriver device. The method according to claim 1,
Wherein the component is selected as a function of the instantaneous rotational frequency from a predetermined set of voltage values,
A method of controlling a discrete screwdriver device. The method according to claim 1,
Wherein the component is determined as a product of the instantaneous rotational frequency and a predetermined coefficient,
A method of controlling a discrete screwdriver device. 4. The method according to any one of claims 1 to 3,
Wherein each voltage of the power supply voltage pulses comprises:
A first term corresponding to a predetermined theoretical constant power supply voltage multiplied by a pulse amplitude coefficient; and
- a second term corresponding to said component dependent on the instantaneous rotational frequency of said rotor
≪ / RTI >
A method of controlling a discrete screwdriver device. The method of claim 4,
Wherein the pulse amplitude coefficient is in the range of 0 to 1,
A method of controlling a discrete screwdriver device. The method according to claim 4 or 5,
Wherein the predetermined theoretical constant supply voltage is a product of a predetermined current value and an electrical resistance of the screwdriver device,
A method of controlling a discrete screwdriver device. The method according to any one of claims 4 to 6,
Wherein the second term is the product of the instantaneous rotational frequency of the rotor and the counter electromotive force coefficient of the motor,
A method of controlling a discrete screwdriver device. The method according to any one of claims 4 to 7,
Wherein said second term considers data stored in the form of a correspondence table associating a plurality of pairs of power supply voltage values and a rotational frequency value of said rotor,
A method of controlling a discrete screwdriver device. The method according to any one of claims 1 to 8,
Correcting a voltage of the power supply voltage pulse of the motor in accordance with detection of an operation abnormality,
A method of controlling a discrete screwdriver device. The method of claim 9,
Wherein the step of detecting the operation abnormality includes:
- measuring the electrical power consumed by the motor;
Comparing the measured value of the electrical strength consumed by the motor with a predetermined threshold value;
- reducing the voltage of the power supply voltage pulse of the motor when the measured value of the electric power consumed by the motor is above the threshold value
/ RTI >
A method of controlling a discrete screwdriver device. The method of claim 10,
Wherein decreasing the voltage of the power supply voltage pulse of the motor is characterized by decreasing the first term of the voltage of the power supply voltage pulse,
A method of controlling a discrete screwdriver device. The method of claim 10,
Wherein the step of decreasing the voltage of the power supply voltage pulse of the motor is characterized by reducing the sum of the product of the first term and the amplitude coefficient and the sum of the second term,
A method of controlling a discrete screwdriver device. An electric motor in which a rotor is connected to a terminal unit that can be rotationally driven, and a power supply means for the motor by a continuous power supply voltage pulse,
The system comprises:
Means for real-time measurement of the instantaneous rotational frequency of the rotor, and
Means for determining a voltage component of the power supply voltage pulse dependent on the instantaneous rotational frequency;
Means for integrating the voltage value dependent on the instantaneous rotational frequency of the rotor to determine the voltage of the power supply voltage pulse in real time;
And means for determining an instantaneous supply voltage of the motor during each of the supply voltage pulses
≪ / RTI >
Discontinuous screw drive system. 14. The method of claim 13,
The means for determining in real time the voltage of the supply voltage pulse comprises:
A first term corresponding to a predetermined theoretical constant power supply voltage multiplied by a pulse amplitude coefficient; and
- a second term corresponding to said component dependent on the instantaneous rotational frequency of said rotor
And means for calculating a sum
Discontinuous screw drive system. 14. The method of claim 13,
And means for correcting a voltage of the power supply voltage pulse of the motor in accordance with detection of an operation abnormality.
Discontinuous screw drive system. 16. The method of claim 15,
The means for detecting the operation abnormality preferably includes:
Means for measuring the electrical strength consumed by the motor;
Means for comparing the measured value of the electrical strength consumed by the motor with a predetermined threshold value;
Means for decreasing the voltage of the power supply voltage pulse of the motor when the measured value of the electric power consumed by the motor is greater than or equal to the threshold value
/ RTI >
Discontinuous screw drive system. 15. The method of claim 14 or 16,
Wherein the means for reducing the voltage of the power supply voltage pulse of the motor comprises means for reducing the first term of the power supply voltage pulse,
Discontinuous screw drive system. 15. The method of claim 14 or 16,
Wherein the means for reducing the voltage of the power supply voltage pulse of the motor comprises means for multiplying the product of the first term and the amplitude coefficient,
Discontinuous screw drive system. 15. A computer program product comprising program code instructions for implementing the method according to any one of claims 1 to 12 when executed on a computer. 20. A computer readable and non-volatile storage medium for storing a computer program product according to claim 19.

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