SE1400226A1 - A system for protecting a human from injury upon collision with a movable object - Google Patents

Description

- Adding compliant material to reduce impact above the actuators reduces the cooling of the motors and gears.

- A capacitive method is unreliable close to metal objects.

- Distributed sensor layer is usually not robust enough in industrial environment Obiect and summary of the invention An object of the present invention is to provide a system for protecting a human from injury upon collision with a movable object, which system overcomes the above mentioned drawbacks with the prior art systems. This object is achieved with a system as defined in claim 1.

The system comprises two rigid parts at least partly separated by a compliant material, at least one sensor adapted to measure deformation of the compliant material, and a control unit adapted to slow down or stop the motions of the object upon detecting a deformation in the compliant material.

When a collision takes place between a part of a human and one of the rigid parts or a shield connected to one of the rigid parts, the compliant material will be deformed. The deformation of the compliant material is detected and reported to the control unit. The control unit slows down or stops the motions ofthe object upon detecting a deformation in the compliant material in order to avoid injury of the human. Different control concepts to reduce the injury can be used, for example, switching to compliant control, reversing the ongoing motion, or just limit the speed of the object.

The movable object is, for example, a robot, a Cartesian manipulator, a mobile platform, an object on a linear track, or other types of manipulators.

The system for protecting human from impact injuries according to the invention will have very low cost since in most cases only one simple position measurement sensor needs be used. The system according to the invention is very robust, also in severe industrial environments, and is independent of the electric or magnetic properties of its surrounding. lt is also very easy and cheap to obtain redundant sensing since low cost local sensors are used and not distributed sensor layers. Moreover, compliant material can be avoided around heat generating parts meaning that for example actuators can run at full power when needed.

According to an embodiment of the invention, the system further comprises at least one element harder than the compliant material and positioned between the two rigid parts to increase the deformation adjacent to the at least one sensor. ln this way the deformation will be enhanced where a sensor is located, meaning higher sensitivity to collisions with human. The harder elements are preferably designed in such a way that it increases the sensitivity in all directions with respect to the direction of the impact.

According to an embodiment of the ínvention, one of the rigid parts is a portion of the object and the other rigid part is mounted around or at one side of said portion of the object. This will make it easy to mount the structure on the object and the other rigid part can be designed to have the same shape as the preserving the outer design of the object.

According to an embodiment of the invention, the other rigid part comprises two halves attached to each other and surrounding said portion of the object. With this possibility it will be very easy to mount the safety arrangement on for example a robot arm. Then it is an advantage also to cut the soft material into two halves, each half glued into a rigid body half.

According to an em bodiment of the invention, the at least one sensor measures a position change caused by the deformation of the compliant material. Examples of low cost sensors that can be used for this are mechanical contacts, a Light Emitting Diode (LED) together with a Photo Diode (PD) or a Hall Element (HE) together with a permanent magnet. The mechanical contact is then arranged to be close when the soft material is not deformed but when a deformation takes place, the position of one electrode of the contact is changed and the connection to the electronic safety system is opened. The LED is arranged in relation to the PD to measure a position change of the soft material due to its deformation, for example the position change of the soft material can reduce an opening for the light beam between the LED and the PD. ln the HE case, the permanent magnet can be glued into the soft material and the HE can be mounted on the other rigid part. When the position of the permanent magnet is changed because of the deformation of the soft material, the HE will sense the change in position of the magnet and the safety system will send a collision message to the object controller.

According to an embodiment of the invention, a shield is mounted on the other rigid part. As mentioned earlier, the soft material does not need to cover the whole space between the rigid parts. Where heat generating sources exist on the object, no soft material is used and in these areas of the object only the other rigid part covers the object. Now there are cases when larger areas need to protected than is protected by the other rigid part and then special shields can be mechanically mounted on the other rigid part. When there is an impact on these shields, the shields will tilt and thus also the other rigid part and as a consequence the soft material will be deformed and the sensor will detect the impact.

According to an embodiment of the invention, the shield is connected via an actuator to the other rigid part. ln this way it is possible to adapt the position and orientation of the shield to where it is needed to protect human from direct collision with the robot. For example the shield can be actuated to cover the tool of a robot when the robot moves in the vicinity of humans and then retract the shield when the robot needs the tool for processing or gripping.

According to an embodiment of the invention, one of the rigid parts is in contact with the floor or an equipment in a robot cell and that the other rigid part is connected to a shield protecting humans from collisions with the object. For example, there are situations when the actuated shield mentioned in the previous text cannot be used during processing or grasping. It will then be an advantage to place a stationary shield arrangement where the risk of a collision between the robot tool and humans is high.

Brief description of the drawings Figure 1 shows an example of a lightweight industrial robot suitable for human robot collaboration and/or fenceless installations.

Figure 2 shows a first example of an arrangement for protecting a human from injury according to the invention. The example is illustrated for the upper arm of the robot in Figure 1.

Figure 3 shows a cross-section cut along a line A-A of the arrangement in Figure 2.

Figure 4 shows a second example of an arrangement for protecting a human from injury according to the invention.

Figure 5 shows a cross section projection of the arrangement in Figure 4.

Figure 6 shows a third example of an arrangement for protecting a human from injury according to the invention.

Figure 7 illustrates the robot shown in figure 1 completely covered with an arrangement for protecting a human from injury according to the invention.

Figure 8 shows two possibilities to use an arrangement according to the invention for protection of tools or objects carried by a robot. By means of actuators the protection can be withdrawn when the tool or object need to interact with its surrounding.

Figure 9 shows another example of an arrangement for protecting a human from injury according to the invention.

Figure 10 shows the interior of the pillar in Figure 9, using the same basic concept of measuring deformation of the soft material as in the previous figures .

Figure 11 shows a more compact sensing unit than in Figure 10 for mounting of a shield.

Detailed description of the invention Figure 1 shows an example of a lightweight robot with high performance using parallel bar for axis 3 to avoid a high inertia from having axis 3 motor, gear and housing on the top of the lower arm. Moreover wrist actuators are implemented as integrated actuation units motor, brake, resolver and gear with high torque to weight ratio. ln the figure the following robot components are outlined: 1. Robot foot 2. Axis 1 3. Housing for gear of axis 2 4. Parallel arm transmission carbon fiber rod to axis 3 at the elbow 5. Elbow joint for parallel bar 6. Elbow joint 7. Housing for gear for driving parallel bar 8. Lower arm, as carbon fiber rod 9. Upper arm, also as carbon fiber rod 10. Servo actuator module for axis 4 11. Servo actuator module for axis 5 12. Servo actuator module for axis 6 13. Mounting flange for tools 14. Elbow part of upper arm 15. Robot controller including redundant hardware and software of safe control. This means that when a collision is detected between robot and human, the robot will reduce its speed or stop and optionally retract to move away from the collision position. 16. Cable for motors and resolvers/encoders 17. Cable for safe communication with sensors exemplified in the upcoming figures. ln order to reduce the injury risk in the case of robot human collaboration or when using robots without fences in a more general term, a low cost robust concept is developed, where the deformation of a compliant material is measured using sensors that measure position. One example of such an arrangement is shown in Figure 2. The safety structure is shown for an upper arm 9 in Figure 1. A rigid shield 20 comprising two halves 20a, 20b is mounted on a part of the upper arm 9 by means of a compliant material 23. The compliant material 23 may also be divides in two halves 23a, 23b. The compliant material is resilient. The two halves 20a, 20b are, for example, made by 3D printing. Each half of the rigid shield 20 has the compliant material 23a, 23b glued to its inner surface and the compliant material is at mounting pressed on to the upper arm 9 or also glued on the arm. Only part of the shield 20 is mounted with the compliant material 23 on the arm and for example the part containing the heat generating axis 4 actuator 10 has no heat isolation layer around its surface but only the rigid shell 20. ln the same way there is no compliant material around the elbow 14, which results in full rotation possibilities of the elbow when the geometry of the shell 20 is adapted to the elbow movement. ln this case the deformation of the compliant material 23 is measured using a sensor including a transmitter 21, a receiver 22 and a flexible tube 24 mounted between the transmitter and receiver. The deformation of the compliant material 23 changes the position of the flexible tube 24 mounted between the transmitter and receiver. When possible there can be a reflector in one end and a combined transmitter and receiver in the other end of the tube. The tube is located in a hole in the compliant material 23 and when a collision takes place between a part of a human and the shell 20, the position of at least a part of the tube will be changed and the transmission efficiency between the transmitter and receiver will be reduced, which will be used to order the robot to stop and retract. ln order to magnify the position changes of the tube, localized geometries with harder material 25, 26, 27 are inserted into the compliant material. The tube material will depend on the type of sensors. For ultrasonic, a sound damping rubber tube can be used or the tube can just be the inner surface of a hole in the compliant material. For optics a black light absorbing tube can be used and for microwaves a tube of suitable electrical resistance. As an alternative a wire can be drawn in the channel and at impact the wire will touch the channel wall, which can be used to obtain an electric contact if the tube is electrically conducting.

Figure 3 shows a cut A-A of the arrangement in Figure 2. lt is here evident that the shell 20 consists of 2 halves 20a, 20b and the arrangement 30 indicates where the halves are mounted together, for example with screws hidden in holes in the shell. Also the borders ofthe 2 compliant material halves 23a, 23b can be seen 31. Example of compliant material is foam of rubber or plastic. The tube for measuring the deformation of the compliant material 24 is in this case parallel with the carbon rod 9. However, it is an advantage to have the tube in a 3 dimensional angle to get good sensitivity for collisions from all directions. lt is also possible to design the hard geometries 26 in a way to get more isotropic collision sensitivity, for example with the angle of the hard geometry 26 in Figure 3.

As mentioned it is possible to have measurement tubes 24 in different directions in the compliant material and when using reflectors it is possible to use tubes in right angles to each other and also in a ZigZag pattern to maximize the sensitivity for impact on the rigid shield in any direction.

There are many ways to measure the deformation of the compliant material by means of position sensing. Thus, Figure 4 shows the case when 2 position sensor arrangements 35 - 38, 39 are used.

The sensor 37 measures the distance to the target 36, which can be made for example by implementing 37 as a Hall Element and 36 as a permanent magnet. 36/37 can also be an optical system with a Light Emitting Diode and a Photo Diode or simply a mechanical contact or a sliding resistor. The part 36 of the sensor arrangement is mounted by the plate 35 in the compliant material 23a and the part 37 is mounted on the shell 20a with the connector 38. The sensor arrangement 39 is mounted in the same way as 36/37 but here sliding parts are used for the sensor instead off face to face parts. lt is also possible to measure the position changes because of the deformation of the compliant material with force- or pressures sensors located as the sensor part 37 but then in direct contact with the compliant material of a rigid part as 35/36 assembled into the compliant material. lf very high precision is needed in the sensing of the deformation of the compliant material, 37 can be an eddy current sensor or a capacitive sensor and 36 a metal target plate. lt could also be possible to use inductive sensors as LVDT:s. The position sensing direction is made to have an angle of about 45 degrees in relation to the normal to the robot arm 9. The rigid part 40 embedded in the compliant material increases the sensitivity for collisions at a direction corresponding to the normal to the figure. 41 is also a rigid part to increase the sensitivity to collisions.

Figure 5 shows that the sensing direction can simultaneously have an angle of about 45 degrees relative the interface 31 between the two halves of compliant material. This figure shows the sensor arrangement in an axial direction of the robot arm 9.

Figure 6 illustrates that the position measurements to detect the deformation of the compliant material can also be made with an angle measurement sensor 45, for example a rotating potentiometer, a resolver or another electromagnetic angel measurement sensor. Here the arm 46 is mounted into the compliant material and measures the position of the material at the end ofthe arm 46. When the position of the tip of the arm is changed the angle ofthe arm will change, which will be sensed by the rotation sensor 45. Here a gap 47 has been made in the compliant material to give place for the sensor 45 and some of the measurement arm 46. The arm should be mounted with about 45 degrees with respect to both the robot arm 9 and the interface between the two halves of compliant material 31, compare Figure 5. 48 represents a rigid geometry to increase the sensitivity for impacts in a direction corresponding to a right angle to the figure plane.

Figure 7 illustrates shells for the complete robot in Figure 1. 56a and 56b are the shells for the actuators of axis 1, 2 and 3. 57a 57b hidden indicates the placement of the compliant material.

As can be seen there is no compliant material covering the motors, where it is not allowed to reduce the cooling efficiency. It should however be emphasized that simultaneously as the shells protect from harmful impacts it also protects from touching hot motors. 60a and 60b with compliant material 61a are the shells for the lower arm and the parallel transmission to the elbow axis. The shells 20a and 20b have already been described. The servo actuators for axis 5 and 6 are protected with the shells 65a and 65b with compliant material 66a and 66b. Here there is a gap between 66a and 66b on the other side of the robot to obtain free access to the mounting flange for all angles of axis 5. As an alternative the shell for the upper arm 20 can be prolonged to cover also axes 4 and 5. A cable between the sensors in the shells are mounted on the inside of the shells and connected with connectors between the shells. The cable is then connected to the safety board of the robot controller. lt is very important to protect human from collision not only with the robot but also with the tool or work object carried by the robot. This is especially important when the robot handles tools or objects with sharp edges. Figure 8 shows two possibilities to extend the shell concept described so far to protection of tools or by robot carried objects without introducing more sensors. ln the first option, a shield 20c is mounted on the shaft 72 that can be rotated by a motor 71. When the robot is for example in a machine for tending there is no risk for collision between humans and the tool and the shield 20 is rotated backwards over the shell 20a. As soon as there is a risk of collision between human and tool the shield 20c is rotated to cover the tool as in the Figure. ln the second option the tool protecting shield 20d is mounted on a linear bearing 75, which is driven by for example a rack and pinion arrangement or a belt arrangement. ln this case the shield 20 d can actually completely surround the tool and be designed as tube which can pass over the shell 20a/20b when the tool does not need any protection. lf the shield 20c or 20d collides with human, the sensor arrangement for detecting deformations of the compliant material will react and stop the robot. Simultaneously the shield 20c or 20d will protect the human for sharp edges. In the figure a micro switch 70 is used to detect position changes of the tip 48 of the arm 46 upon deformations of the compliant material.

There are however cases when it is not possible to use shields on the robot like those in Figure 8 because the robot must have the tool free simultaneously with the risk that humans are in the vicinity of the robot tool. Examples of this are when the robot fetches objects from a table or a conveyor or when the robot needs to perform processes as welding or gluing on objects that can be reached by humans. ln these cases there are usuallyjust smaller areas that must be protected for unexpected collisions between robot tool and human and a sensor-based shield as outlined in Figure 9 can be used. Here the same concept as in Figure 8 is used with a shield 83, can also be implemented as a double layer shield with compliant material in between to reduce the impact between robot and human connected to a shell 20 mounted around an inner tube 9 using compliant material and with at least one sensor detecting deformation of the com pliant material. ln the case of Figure 9 the shield 83 is not actuated to be withdrawn as in Figure 8, even if this is possible. One solution is to have for example a horizontal linear actuator mounted on 80 in order to follow the movement of the robot tool and make protection over a larger area than covered by the shield when it is stationary as in Figure 9. The inner tube 9 is mounted on a foot 82. 81 indicates an optional shield mounting on the shell 20 making it impossible to move the foot without sensor detection and stop of robot. 80 is a mounting interface for the shield, making it possible to use different shield geometries for the same pillar type arrangement. Of course all the types of sensor arrangements discussed above can be used here too.

Figure 10 exemplifies the pillar arrangement, compare the upper arm shields in Figures 2 - 6 and 8. The inner tube 9 is mounted on the foot 61 and between the tube 9 and the shell parts 20a, 20b are the compliant material parts 23a and 23b. Here a double ball bar 86 2 serially mounted ball and socketjoints is introduced between the inner tube 9 and the shell 20 in order to increase the sensitivity to compliant material deformation using only one sensor 85 in the top of the tube 9. The sensor can be of any type to measure position changes of the shell 20 in relation to the tube 9 because of deformations of the compliant material 23 caused by impacts on the shield mounted on the mounting plate 80. In the figure a pin hole optical sensor with a Light Emitting Diode, a pinhole and at least 3 photo diodes or a lateral photodiode to measure movements in all directions in the horizontal plane.

Figure 11 shows that it is possible to obtain a more compact sensing unit on which shields can be mounted. Here the foot 61 corresponds to the inner tube 9 in Figure 10 and there is only one shell part 20a and one compliant material part 23a. Preferably the compliant material is glued both on the shell 23a and on the foot 61. The sensing of the position changes because of deformation of the compliant material is here made with an electrical contact 97, which will open the electrical circuit between the wires 90 and 91. A wire 93 is electrically conducting as well as its mounting pin 97 and the foot 61. The mounting pin 92 is an insulator. The wire 93 is mounted through the holes 98 in the bars 94 and 95. When the compliant material is deformed the position of any of the bars 94 and 95 will change and the wire will stretch the spring 96 and the contact 97 will disconnect the electrical current through the wires 90 and 91.

Claims (10)

10 A system for protecting a human from injury upon collision with a movable object, the system comprising two rigid parts (20a-b,9) at least partly separated by a compliant material (23,23a-b), and a control unit (15) adapted to control the motions of the object, characterized in that the system further comprises at least one sensor (21-24- 22,24;35-38,39;45-56;46-70;85;92-98) adapted to measure deformation of the compliant material, and the control unit is adapted to slow down and/or stop and/or reverse the motions of the object upon detecting a deformation in the compliant material. .

The system according to claim 1, wherein the system further comprises at least one element (25-27;40-41;48;) harder than the compliant material (23,23a-b) and positioned between the two rigid parts (20a-b,9) to increase the deformation adjacent to the at least one sensor (21-24-22,24;35-38,39;45-56;46-70;85;92-98). .

The system according to any of the previous claims, wherein one of the rigid parts is a portion (9) of the object and the other rigid part (20a-b) is mounted around said portion of the object.

The system according to claim 3, wherein the other rigid part (20a-b) comprises two halves attached to each other and surrounding said portion (9) of the object. .

The system according to claim 3 or 4, wherein the compliant material forms two halves (23a,23b). .

The system according to any of the previous claims, wherein the at least on sensor (21-24-22,24;35-38,39;45-56;46-70;85;92-98) measures a position change caused by the deformation of the compliant material. .

The system according to any of the previous claims, wherein a shield (20c,20d,83) is mounted on one of the other rigid parts (20a-b,9). .

The system according to claim 7, wherein the shield (20c,20d) is connected via an actuator (71;75) to the other rigid part. 11

9. The system according to any of the previous claims, wherein the one of the rigid parts (20a-b,9) is in contact with the floor or an equipment in a robot cell and that the other rigid part is connected to a shield (83) protecting humans from collisions with the object.

Ansökningsnummer: 1400226-5 I denna ansökan saknades patentkrav vid ingivningen.