Patent Application
20210187680
This application which claims benefit of Serial No. 2019904851, filed 20 Dec. 2019 in Australia and Serial No. 2020900390, filed 12 Feb. 2020 in Australia and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.
This invention relates to a compliant tool carrier.
Tools are used for performing various operations. Tools may be carried on tool carriers. Tool carriers may be mounted to robot arms. It may be useful for tool carriers to be compliant to external forces to prevent tools from damaging workpieces, prevent damage to tools, and to allow tools to passively follow the profile of part of a workpiece.
Some tool carriers may be complex and have many degrees of freedom. Some tool carriers may use active feedback control systems and powered actuators to control their movement in response to external forces. Such tool carriers can be expensive and require complex control systems.
According to one example embodiment there is provided a tool carrier comprising:
Embodiments may be implemented according to any one of the dependent claims 2 to 14.
It is acknowledged that the terms “comprise”, “comprises” and “comprising” may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning—i.e., they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements.
Reference to any document in this specification does not constitute an admission that it is prior art, validly combinable with other documents or that it forms part of the common general knowledge.
The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention.
The blade carrier 1 includes a base 2, a blade mount 3 and a linkage 5. The blade mount 3 holds a blade 4. The linkage 5 is one example of a mechanical assembly providing a mechanical constraint on the blade mount 3 to constrain it to be in a substantially constant orientation.
The linkage 5 is arranged to allow the blade 4 to translate in two directions while staying at a fixed angle to the base 2. The blade mount 3 is separated from the base 2 in one direction. The blade mount 3 can translate in directions transverse to this direction of separation. Keeping the blade 4 at a fixed angle may be useful when cutting or scraping meat from bones. The translation of the blade mount 3 allows it to be compliant in these two directions. In particular, when a force is applied to the blade mount from an external object, the blade mount can comply to some degree to this force by moving in the direction of the applied force. This compliance may be useful when cutting or scraping meat from bones by allowing a blade to “ride” along the bone and follow its profile without the need for active control of the blade's position based on feedback or position measurements.
The linkage 5 is a parallel motion linkage. The linkage includes parallel rods 6, 7 and 8 arranged in a prism. In particular, the ends of the rods 6, 7 and 8 define the vertices of the prism. The rods extend along edges of the prism between the two parallel polygonal ends of the prism to form parallelograms between each pair of rods. In particular, the ends of the pairs of rods define the vertices of the parallelograms. The ends of the rods 6, 7 and 8 are pivotally coupled to the base 2 and the blade mount 3 by universal joints 11 (only one of which is indicated). The universal joints 11 provide the rods 6, 7 and 8 with two rotational degrees of freedom.
Because the rods 6, 7 and 8 are pivotally coupled with two degrees of rotational freedom, the blade mount 3 can move in two different directions with respect to base 2. The parallel linkage formed by the rods 6, 7 and 8 ensures that the polygonal ends of the prism remain parallel with each other during this movement and the blade mount 3 stays in a substantially fixed orientation with respect to the base 2. Because the blade 4 is held by the blade mount 3, the blade 4 stays at the same angle to the base 2 during this movement. In this example, there are three rods 6, 7 and 8 and the prism is a triangular prism, although more rods could be used to form prisms with more sides.
Alternative connections between the base and the tool mount could be used to allow compliance in two directions while remaining at a fixed angle. For example, an X-Y guide having two transverse rails could be provided between the base and the tool mount. In the X-Y guide, one of the rails would be able to slide on the other and one or both of the base and the tool mount would be able to slide along a respective rail. The combination of sliding movements in the two directions would allow the tool mount to comply in the plane of the rails while remaining in a fixed orientation. In another example, roller bearings movable on a planar bearing surface could be provided between the base and the tool mount to allow compliance in two directions.
As shown in
As shown in
The movement of the blade mount 3 may be controlled by pneumatic cylinders 9 and 10. The cylinders 9, 10 are connected to the rod 6 by sleeves 12 and 13, respectively. The cylinders 9, 10 are connected to the base 2 by universal joints 11 to provide them with two rotational degrees of freedom. The cylinders 9 and 10 each lie at a non-zero angle to the rods 6, 7 and 8. The cylinders 9 and 10 are also of variable extension. To allow the blade mount 3 to translate with respect to the base 2, the extension of at least one of the cylinders 9 and 10 can change.
The cylinders 9, 10 are arranged at a non-zero angle to each other. This allows them to control movement of the blade mount 3 in different directions. In one example, the attachment points of the cylinders 9 and 10 and the rod 6 to the base 2 form a right-angled triangle with the attachment point of the rod 6 being opposite the hypotenuse and the attachment points of the cylinders 9 and 10 being at 90° to each other about the attachment point of the rod 6. This may ensure that the cylinders 9, 10 control the movement of the blade mount 3 largely in different directions for optimal control.
By adjusting the resistance of the cylinders 9 and 10 to changes in extension, the compliance of the blade mount 3 (and therefore the blade 4) to external forces can be adjusted. The resistance to changes in extension may be adjusted by changing the pressure in one or both of the pneumatic cylinders 9, 10. The pressure in each cylinder can be controlled independently of the pressure in the other cylinder to control the compliance in different directions separately. The cylinders 9, 10 can be connected to an external source of pressurised gas and to a pressure release vent to allow the pressure in the cylinders 9, 10 to be increased or decreased as needed.
Using cylinders allows the blade mount 3 to passively comply to forces. Because the cylinders have a relatively low resistance to movement of the blade mount at or near its rest position, they will be naturally quite compliant to movement from this position. This obviates the need for a control system that actively drives or allows movement of the blade mount in the same direction as an applied force.
Alternatively, springs or other compliant elements could be used to provide the blade mount with compliance.
The movement of the blade mount 3 (and therefore a mounted blade) can also be driven by controlling the extension of the cylinders. By controlling the pressure in one or both cylinders, the extension of that/those cylinder(s) can be controlled between extended and retracted positions. The cylinders 9, 10 may be able to be controlled to partly extended positions.
As shown in
Alternatively, linear actuators or other actuable elements could be used to move the blade mount between different positions.
The blade carrier 1 can be used with a robotic system such as a meat processing system. In particular, it can be mounted to a robot arm at the base 2. The robot arm can move the blade carrier 1 into a desired position and orientation for cutting or scraping meat from a bone. The position of the blade mount 3 relative to the base 2 can also be controlled based on the operation to be performed (cutting or scraping). The blade can then be used to cut the meat or scrape it from the bone, while being compliant to forces acting on the blade. This means that the blade will be deflected (along with the blade mount) substantially in the direction of a force applied to it. This force may be due to the blade encountering bone in a meat processing example. The blade may then follow or “ride on” the bone while remaining at a substantially constant angle.
Robotic systems are typically automated to perform operations based on known geometry of workpieces. In some applications, workpieces can have a range of sizes, shapes and structures that need to be taken into account by the system. For example, in a meat processing context sections of carcass of different animals can have different sizes, shapes and bone structure. The tool carrier can allow a robotic system to be programmed with a standard set of instructions based on a theoretical average or otherwise representative section of carcass. This could define a standard path or set of movements of a blade mounted to the tool carrier. The compliance of the blade carrier would allow the blade to deviate from a standard path or movement to account for the specific geometry of the section of carcass being processed. This may allow an automated system to be programmed according to a simple set of standard instructions while the blade carrier passively complies to the size, shape and structure of the section of carcass being processed to tailor the processing to each section of carcass.
In this example, the tool carrier 20 includes a base 22, a tool mount 23 and a linkage 25 that couples the base 22 to the tool mount 23. The linkage 25 includes a parallel motion linkage made up of rod—in the form of an arm 26—and rods 27 and 28. The rods 27 and 28 are coupled to the base 22 by ball and socket joints 32 and to the tool mount 23 by ball and socket joints 31. The arm 26 is coupled to the base 22 by universal joint 34 and to the tool mount 23 by universal joint 33. Universal joint 34 is made up of a pair of swivels 35 and 36 and universal joint 33 is made up of a pair of swivels 37 and 38.
The movement of the tool mount 23 is controlled by cylinders 29 and 30 (partly obscured). In this example, cylinder 29 acts on arm 26 part way along its length to control the movement of the tool mount 23 in one direction—approximately left-right in
The cylinder 30 acts on arm 26 near its connection to the base (via swivel 35) offset from the midline of the arm 26 to control movement in another direction—approximately up-down in
Because the arm 26 and rods 27 and 28 form a parallel linkage, the rods 27 and 28 also pivot when the arm 26 pivots while remaining parallel to each other. This means that the tool mount 23 translates while remaining in a substantially fixed orientation with respect to the base.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant's general inventive concept.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019904851 | Dec 2019 | AU | national |
| 2020900390 | Dec 2020 | AU | national |
