GB2225651A

GB2225651A - Speed control of a robot

Info

Publication number: GB2225651A
Application number: GB8922350A
Authority: GB
Inventors: Richard James Goodridge
Original assignee: GEC Electrical Projects Ltd
Current assignee: GE Power Conversion Brazil Holdings Ltd
Priority date: 1988-10-04
Filing date: 1989-10-04
Publication date: 1990-06-06
Anticipated expiration: 2009-10-04
Also published as: GB8823219D0; GB2225651B; GB8922350D0

Abstract

In a system for mass producing garments, shaped pieces of fabric (19) are fed through sewing positions (6,7) by gantry robots (1-4). At each sewing position the fabric is fed through the sewing machine at a required speed and with a required orientation by a gripper (10-13) which is moved linearly and rotationally by the robot, but at the sewing machine needle the fabric is moved by the sewing machine itself, in dependence upon the needle speed. The required robot speed and orientation for each operation are stored and are controlled by the system software. However, the actual sewing speed at any instant may not be correct for the programmed robot speed, because the sewing machine may have to reduce its speed for a fault condition, such as the needle overheating. The actual sewing speed is therefore monitored, and the robot speed controller (14-17) is operable, if the actual sewing speed does not correspond to the programmed sewing speed, to modify the actual robot speed, so that <IMAGE> <IMAGE>

Description

Manufacturing Process Control This invention relates to the control of manufacturing processes, and particularly to the speed control of automatic equipment for sewing pieces of fabric to form garments or other articles.

Garments, such as underclothes and blouses, have previously been manufacturered by passing suitably-shaped pieces of fabric ("cut parts") to a machinist, who then overlays and/or folds them as required, and passes them manually through a sewing machine. The machinist forms seams, binds the edges of the cut parts and adds lace and elasticated waistbands, where necessary. The accuracy of the positioning of the seams relies on the machinist's skill, and nominally-identical garments can finish up having quite a wide range of different sizes and shapes.

Systems have been proposed for automating at least a part of the manufacturing process by using a robot to move a cut part to a work station, such as a sewing machine. The movement of the cut part is effected by a "gripper" which is mounted on the output shaft of the robot, and which makes contact with the upper surface of the cut part.

It is an object of the present invention to provide an iirroved method and apparatus for controlling the speed of operation of a robot feeding a cut part to a sewing machine and the sewing speed of the sewing machine.

According to one aspect of the invention there is provided a method of simultaneously controlling the speed of movement of a robot feeding a piece of fabric to a sewing machine and the sewing speed of the sewing machine, wherein a speed controller is programmed to achieve a desired robot feeding speed and a desired sewing speed; either or both of which may be required to vary from time to time; wherein the actual sewing speed is monitored; and wherein if the monitored actual sewing speed at any instant does not correspond to the programmed sewing speed the actual robot speed is modified in accordance with the equation actual robot speed = programmed robot speed actual sewing speed programmed sewing speed According to another aspect of the invention there is provided apparatus for sewing a piece of fabric, comprising a sewing machine; a robot for feeding the piece of fabric to the sewing machine; means for monitoring the actual sewing speed; and speed control means programmed to control the feeding speed of the robot and the sewing speed in acordance with a desired robot feeding speed and a desired sewing speed, respectively, either or both of which may be required to vary from time to time, the speed control means being operable if the monitored actual sewing speed does not correspond to the programmed sewing speed to modify the actual robot speed in accordance with the equation actual robot speed = programmed robot speed actual sewing speed programmed sewing speed An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, which is a schematic plan view of part of an apparatus for the automatic manufacture of garments.

Referring to the drawing, a garment manufacturing system comprises a number of robots, such as robots 1-4, which are used to move shaped pieces of fabric ("cut parts") round on a work table 5.

The cut parts have to be moved into position at work stations, such as manipulators and sewing machines, for a sequence of folding, overlaying and sewing operations to be performed. As an example, two sewing machines 6 and 7 and two manipulators 8 and 9 are shown, but any other combination of work stations may be involved.

The robots are preferably of the gantry type in which a robot is mounted to slide along a first overhead rail or pair of rails, which, in turn, is mounted to slide along a second overhead rail or pair of rails, orthogonal to the first rail or rails, so that the robot can be moved in x and y directions relative to the table. The output shaft of the robot is substantially vertical and is arranged for upward and downward movement (z motion) and rotation (&commat; notion) about its vertical axis. For the sake of clarity of the drawing, the overhead rails are not shown.

The movement of a cut part is effected by a "gripper", such as the grippers 10-13, which is mounted on the output shaft of the robot, and which makes contact with the upper surface of the cut part, so that movement of the robot causes the cut part to slide on the table to the required position.

Each robot 1-4 is controlled by its respective controller 14-17, but the overall control of the robots is effected by a system controller 18, in accordance with a process control program and taking into account indications from devices which monitor the progress of the manufacturing operations. Each sewing machine and manipulator is also controlled by the system controller 18.

Let us assume that a cut part 19, which has been taken from a stack 20 and has been placed on the table 5 by a ply separator and feeder 21, has firstly to be bound at its edges. The syste controller 18 causes the robot controller 15 to move its robst 2 into position over the cut part and to lower its gripper 11 accurately into position on the cut part. The robot then moves the cut part to the sewing machine 6 and adjusts the position and orientation of the cut part while it is being fed through the sewing machine. The edges of the cut part are thereby bound. A waistband may also be attached to the cut part at that stage.

Data for controlling the speed and coordinates for the various robot movements and the sewing speed are produced of--line at a separate computer terminal comprising a processor 23, a visual display unit 24 and a keyboard 25. A link 26 is provided between the off-line programming system and the system controller 18 to enable data for any particular style or size of garment to be loaded into the system controller 18.

The sewing machine 6 has its own feed device 27 for feeding the fabric under the needle at a speed which is synchronised with the downward and upward oscillations of the needle. The gripper has to move the cut part to a position where the feed device 23 can take over the feeding of the cut part during the sewing operation, and the robot must continue to move the cut part, turning it and guiding it, as necessary, as would the hands of a human machinist, so that the seam follows a predetermined line.

It will be apparent that the speed of movement of the cut part by the robot must, at all times, be such that the fabric is fed to the feed device 27 at the speed required by that device. If the robot feeding speed is too high the material will become cobbled, and if it is too low the stitch size will be incorrect and the thread will become looped and knotted.

Although the desired speed of feeding by the robot and the desired sewing speed will have been determined off-line for every instant of the sewing operation and will be contained in the software of the system controller 18, it is possible that the actual sewing speed may not remain at its programmed level. For example, it may be necessary for the sewing machine to reduce its speed due to some fault condition, such as the needle overheating. In particular, the sewing of curved seams as well as straight seams presents problems.

Hence, in the present system the actual sewing speed is continuously monitored by a device 28, and an indication of the actual speed is fed back to the system controller 18. The system.

controller then operates to modify the robot speed, whenever necessary, to maintain the following relationship: actual robot speed = programmed robot speed actual sewing speed programmed sewing speed Although the above embodiment is described as relating to garment manufacture, it will be apparent that the method and apparatus of the present invention may be used in relation to any fabric sewing operation.

Claims

1. A method of simultaneously controlling the speed of movement of a robot feeding a piece of fabric to a sewing machine and the sewing speed of the sewing machine, wherein a speed controller is programmed to achieve a desired robot feeding speed and a desired sewing speed; either or both of which may be required to vary from time to time; wherein the actual sewing speed is monitored; and wherein if the monitored actual sewing speed at any instant does not correspond to the programmed sewing speed the actual robot speed is modified in accordance with the equation actual robot speed = programmed robot speed actual sewing speed programmed sewing speed

2. A method of controlling the sewing of a piece of fabric, substantially as hereinbefore described with reference to the accompanying drawing.

3. Apparatus for sewing a piece of fabric, comprising a sewing machine; a robot for feeding the piece of fabric to the sewing machine; means for monitoring the actual sewing speed; and speed control means programmed to control the feeding speed of the robot and the sewing speed in acordance with a desired robot feeding speed and a desired sewing speed, respectively, either or both of which may be required to vary from time to time, the speed control means being operable if the monitored actual sewing speed does not correspond to the programmed sewing speed to modify the actual robot speed in accordance with the equation actual robot speed = programmed robot speed actual sewing speed programmed sewing speed

4. Apparatus for sewing a piece of fabric, substantially as hereinbefore described with reference to the accompanying drawing.