Integrating electronic and mechanical components to create an adaptive battery tool

The article presents the authors’ approach to the development of a special adaptive tool with an autonomous energy source for tightening screws into threaded holes. The tool allows one to tighten and control threaded connections according to the assembly sequence of the device. A distinctive feature is its independence from the qualifications of the assembler, allowing to reduce the number of defects when assembling products.


Introduction
In modern production two types of tools for screwing and checking threaded connections are currently most widespread: pneumatic and electric tools.Pneumatic tools require constant monitoring after tightening the assembled product, high energy costs due to the operation of the compressor to supply air to the high-pressure line and complex technological air preparation, a separate room for the compressor due to the high noise level it creates during operation.Thus, to reduce energy costs and increase mobility and maneuverability during work, companies often switch to electric torque tools, but due to their versatility and the associated increased requirements for the assembler, they cannot be used in assembly operations with increased screwing control.
To ensure control and automation of the assembler's actions the design of a special adaptive tool has been proposed.It will allow monitoring the actions of the assembler during screwing with the possibility of repeated control.
The adaptive tool being developed, which can be used to both tighten and loosen screws, is an easyto-assemble pistol-type screwdriver designed on an open platform.This design allows the operator to avoid awkward wrist positions when assembling the product, and to track the location of the screws being screwed using optical vision.The adaptive screwdriver model includes: a planetary gearbox, a DC electric motor, a microcontroller control system and a system for remote monitoring and control of the screwdriver.Additional components, such as an LCD display, are located on the tool body and serve to display information such as torque, rotation speed and other information required by the assembler during operation.
Ergonomics and ease of use using an adaptive tool have been studied in the works [1,2,3], these works allow for research to develop a better ergonomically efficient design [1].Conducted studies of the properties of a similar tool show their influence on the usefulness, well-being and quality of work of the operator [2].The work [3] describes the static and dynamic forces that arise during the operation of the tool, influencing the movement of the muscles of the lower part of the arm.The following four articles show the ideas that are implemented to make the tool perfect [4].The paper presents a method for determining the position of a screw using computer vision [5].These developed star gear screwdrivers use TIPS principles [6].The block diagram of a conventional cordless screwdriver is shown in Figure 1.As a rule, in such a screwdriver, the motor current is regulated by a PWM controller built into the screwdriver button, the degree of pressing of which changes the duty cycle of the pulses supplied to the motor, thereby changing its current.Changing the direction of rotation in such a screwdriver occurs by changing the polarity on the motor using a mechanical switch.And the maximum torque on the output shaft of such a screwdriver is limited by a discretely adjustable mechanism.Therefore, a regular screwdriver does not have any control for quality assembly.

Results and discussion
The work proposes one of the ways to increase productivity and quality when assembling a product.It is an adaptive screwdriver with a low cost, including an LCD display for assessing torque, monitoring the speed and position in space of the screw.The bulk of the cost of a Smart Torque Screwdriver comes from the rotary torque sensor, which is used to measure torque in continuous motion.
The adaptive screwdriver has a built-in speed sensor that allows you to measure the number of shaft revolutions per minute.The sensor is made on a Hall element, reacting to the magnetic field of permanent magnets mounted on the intermediate shaft of the gearbox.Signals from the Hall element are sent to a microcontroller, which converts them into rpm.The 3D model of the adaptive screwdriver is designed in solid modeling software, as shown in Fig. 2a and fig.2b in assembled form and in crosssection, respectively.All components installed in the Adaptive Screwdriver can be seen in the cutaway model, including the electronic components and mechanical components used in the tool.Experiments obtained and described in [7] show that the time spent by the operator on tightening screws using an adaptive screwdriver is on average two times less than with a conventional hand tool.
In the process of work, two versions of adaptive structure screwdrivers were developed, which are presented in Fig. 4 and Fig. 5.
In the first version (Fig. 4), the controls of a conventional screwdriver were retained, but a battery current limiting system was additionally added, which is made on the VT1 control element, the DA1 operational amplifier and the current sensor.The maximum current setting is set by the microcontroller through a DAC digital-to-analog converter.In addition to setting the current setting, the microcontroller indicates the state of the screwdriver using the Led module light indication, made on WS2812B addressable RGB LEDs.The NRF module communicates with a stationary control device, which is connected to the control computer via the USB protocol.Through a wireless communication channel, the microcontroller of the adaptive screwdriver receives the value of the current setting and transmits the actually achieved value, which is already converted into a torque value in the microcontroller of the stationary control device and transmitted to the control computer.To power all additional equipment, a DC/DC converter was added to the adaptive screwdriver, which is powered by the adaptive screwdriver's battery.In this version (Fig. 4) when the power to the current limiting system is turned off, the adaptive screwdriver can be used like a regular screwdriver.
The second version of the adaptive screwdriver (Fig. 5) involves a complete replacement of the controls of a conventional screwdriver, which eliminates the possibility of using it in this mode when the power to the microcontroller part is turned off.
In this version, the microcontroller regulates not only the maximum motor current setting, but also stabilizes the voltage on the motor, and accordingly its speed.This approach allows you to programmatically set screw screwing patterns, which ultimately improves the quality of the assembly.
The second version uses a Wi-Fi module as a wireless communication module, which allows you to receive commands and settings directly from the control computer.In addition to the Led module, an LCD screen has been added, which displays the current status of the Smart screwdriver and the necessary information for the assembler.
To reverse rotation, the motor is connected to a bridge formed by transistors VT1-VT4.Changing the direction of rotation of the motor also occurs upon command from the microcontroller using a MOSFET driver.
If any technological operation requires changing the direction of rotation of the screwdriver motor, then when using such an adaptive screwdriver, the assembler will not have to waste time on mechanically switching the direction of rotation.This procedure can be included in the screwdriver cyclogram for this technological operation, which will speed up the process of its implementation.
The moment the adaptive screwdriver starts working is determined by the assembler using the S1 button.While the button is pressed, the screwdriver executes the cyclogram embedded in it.Upon completion of the next step of the cyclogram, the screwdriver will stop and signal that a transition to the next step of the cyclogram is required.To move to the next step of the cyclogram, the button must be released and pressed again.If the button is released before the completion of the cyclogram step, the screwdriver will stop and signal an error in executing the cyclogram.

Conclusion
An adaptive screwdriver is effective and will be useful because it prevents assembly errors.It saves about 50% of the assembler's working time by automatically tracking the location and size of the screw being screwed in and controlling the torque both during the screwing process and when it reaches its maximum regulated tightening torque, which will increase productivity and labor.

Figure 1 .
Figure 1.Block diagram of a conventional cordless screwdriver.

Figure 2 .
Figure 2. 3D model of an adaptive screwdriver: a-assembled; b-in section.

Figure 3 .
Figure 3. Exploded view of a 3D model of an adaptive screwdriver.