Actuated Presser-Foot for Industrial Sewing Machines

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Actuated Presser-Foot for Industrial Sewing Machines

Practical tests have shown that this controller’s action is very similar to the simple reference switching solution. It has been noticed that the force output signal does not suffer the same abrupt variations at reference switching points. This is due to the fuzzy force offset control, that is able to anticipate the force needed for a new number of plies or sewing speed.Although the behavior of these new control solutions have shown to be most interesting, the actual value in terms of fabric feeding efficiency (and thus stitch quality) is still dependent on a correct determination of references for each fabric, number of plies and sewingspeed, to tune the fuzzy logic blocks. In the cases presented, they were established by careful laboratorialIn order to define the parameters for the controllers, some tests were carried out varying the sewing speed and the force output independently.The displacement of the presser-foot was measured during these tests, for a range of sewing speeds and presser-foot forces. Fig. 12 and Fig. 13 display the outcome for two different fabrics (rib and interlock respectively). The graphs show how displacement varies with force and speed, while sewing just two plies of each fabric. Based on these data, almost all the parameters for controller tuning can be extracted automatically. Using signal processing techniques developed in [4], it is possible to determine the point at which presser-foot bouncing ceases to occur This marks the upper limit of the admissible displacement. The lower limit is obtained using the highest force that can be exerted by the actuator. One way of defining the displacement reference can then be the average of these two values. This setting may then be readjusted by the user, or the user can determine the best setting by performing a simple test to determine the maximum force that can be exerted by the presser-foot without damaging the fabric or otherwise producing undesirable results. This may be accomplished very easily at low speed, by producing a seam starting with a very low and ending in a very high force.Once the ideal displacement is defined, the corresponding force will be used as force offset for a specific number of plies and sewing speed.The displacement ranges for recognition of the number of plies are then set as margins around the displacement references previously determined. The correct setting of these margins is fundamental for a proper operation of the system. The ranges are defined by the maximum and minimum displacements determined previously, for each number of plies. If these ranges do not overlap, they can be set as reference switching margins. If they do overlap, the detection margins have to be narrower. In this situation, it is possible that the number of plies may be misinterpreted by the controller. However, this would only happen in extreme situations that most probably result from defect situations. According to this principle, unknown fabrics can be easily defined and saved in a database for future usage. The PID controller has a much less important role in this control system, only compensating for small differences. It is possible that its control parameters can be the same for all situations without affecting the overall performance of the controller, but this has to be confirmed in further testing.Ultimately, the PID controller can be completely eliminated, basing all of the control on the fuzzy blocks.VS Sewing Machines

Actuated Presser-Foot for                                        Industrial Sewing Machines

This marks the upper limit of the admissible displacement. The lower limit is obtained using the highest force that can be exerted by the actuator. One way of defining the displacement reference can then be the average of these two values. This setting may then be readjusted by the user, or the user can determine the best setting by performing a simple test to determine the maximum force that can be exerted by the presser-foot without damaging the fabric or otherwise producing undesirable results. This may be accomplished very easily at low speed, by producing a seam starting with a very low and ending in a very high force.Once the ideal displacement is defined, the corresponding force will be used as force offset for a specific number of plies and sewing speed.The displacement ranges for recognition of the number of plies are then set as margins around the displacement references previously determined. The correct setting of these margins is fundamental for a proper operation of the system. The ranges are defined by the maximum and minimum displacements determined previously, for each number of plies. If these ranges do not overlap, they can be set as reference switching margins. If they do overlap, the detection margins have to be narrower. In this situation, it is possible that the number of plies may be misinterpreted by the controller. However, this would only happen in extreme situations that most probably result from defect situations. According to this principle, unknown fabrics can be easily defined and saved in a database for future usage. The PID controller has a much less important role in this control system, only compensating for small differences. It is possible that its control parameters can be the same for all situations without affecting the overall performance of the controller, but this has to be confirmed in further testing.Ultimately, the PID controller can be completely eliminated, basing all of the control on the fuzzy block,Several controllers have been designed, prototyped and tested to control the feeding system. The efficiency of the speed-variable force control depends on the correct adjustment of the speed-force relationship. From this point of view, the PID controller presents a clear advantage, in which the force applied by the presser-foot is varied depending on the error computed between the maximum presser foot displacement values measured and the reference value. The measurement of presser-foot displacement also enables monitoring of the sewing process, providing the detection of sewing defects, such as wrinkles or folds. A combined PID/Fuzzy logic controller has been proposed, to provide a reference and force offset adaptation to the number of plies and sewing speed. Finally, the latest developed controller also includes a “teach-in” procedure to tune the controller’s parameters while varying sewing speed and the force output independentlyControllers based on a combination of PID/Fuzzy logic control were tested and seem to perform as expected. An exact evaluation of the ideal architecture, in terms of the final seam quality, will be undertaken in future work. This study should also include the possibility of a controller entirely based on fuzzy logic.Another important aspect is the development of procedures for preliminary sewing tests (“teach-in” procedures) and quality. Future work will be focused on these two aspects. In all cases, the control system is still somewhat limited due to the dynamic response of the actuator. Future developments in the field of actuators willcertainly allow a further improvement of the feeding system behavior. The developments carried out on the design of specific controllers for the sewing process represent a further step towards more efficient sewing machines. Although other steps are needed to accomplish the team’s full objectives, this work is a very significant contribution to eliminate trial-and-errortuning of the sewing machine, towards a highly flexible and controlled operations.https://www.vssewingmachine.in/

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