A method of measuring robot tools impact injury level risk with the use of artifacts maximum stress and method of tool design for safer robot operations

Abstract

A method of designing robot tools and parts includes the steps of determining a plurality of von Mises maximum impact stresses as a function of fillet radius of a family of robot tools of same shape and size; determining a lowest von Mises maximum impact stress from the plurality von Mises maximum impact stresses; and selecting a fillet radius for a robot tool based on the determined lowest von Mises maximum impact stress.

Description

[0001] A METHOD OF MEASURING ROBOT TOOLS IMPACT INJURY LEVEL RISK WITH THE USE OF ARTIFACTS MAXIMUM STRESS AND METHOD OF TOOL DESIGN FOR SAFER ROBOT OPERATIONS

[0002] Related Applications

[0003] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 642,146 (filed May 3, 2024), which is herein incorporated by reference in its entirety.

[0004] Federally-Sponsored Research and Development

[0005] This invention was made with United States Government support from the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce. The Government has certain rights in this invention.

[0006] Copyright Notice

[0007] This patent disclosure may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves any and all copyright rights.

[0008] Field of Invention

[0009] The present invention relates generally to tool design, and more particularly to a method of designing tools to minimize human injury.

[0010] Background

[0011] Robots have found applications in many fields of human activities, like industrial manufacturing, hospital services and medical operations, home service, military, etc. The largest percentage of robots are used for manufacturing operations, although exemplary methods and instrumentations, can be adapted to be used for any type of robots. Unfortunately, a US-OSHA report shows that from 1987 until 2021 , industrial robots were responsible for approximately one individual human fatality per year, and one human injury, every two years, in the US alone.

[0012] Summary of Invention

[0013] Provided herein is a discussion of instrumentation, impact artifacts, mathematical modeling, and a stress analysis method, which allow the measurement of robot tools injury level risk and preferred tools geometry design rules, with possible extension to other relevant human activities. The term robot tools also include fasteners, such as pins, commonly used for mounting parts on casings manipulated by — usually industrial — robots; robot parts, such as end effectors, wrists, arms, etc.; and the like.

[0014] According to an aspect of the invention, a method of designing robot tools and parts includes the steps of determining a plurality of von Mises maximum impact stresses as a function of fillet radius of a family of robot tools of same shape and size; determining a lowest von Mises maximum impact stress from the plurality von Mises maximum impact stresses; and selecting a fillet radius for a robot tool based on the determined lowest von Mises maximum impact stress.

[0015] Optionally, the step of selecting a fillet radius for a robot tool includes selecting a tool fillet radius from a look-up table.

[0016] According to another aspect of the invention, a method of predicting a preferred fillet radius tool includes the steps of identifying a preferred geometry for a first tool shape; and predicting a preferred fillet radius of a second tool shape based on the first tool shape using a linear scale rule.

[0017] According to another aspect of the invention, a method of measuring robot tools impact injury level risk includes conducting an impact test with a tool shape on a skin artifact and a muscle artifact; calculating a von Mises maximum impact stress for each of the muscle artifact and skin artifact; and evaluating injury risk based on the von Mises maximum impact stresses.

[0018] Optionally, the step of conducting an impact test with a tool shape on a skin artifact and a muscle artifact includes conducting a first impact test with a tool shape on a muscle artifact; and conducting a second impact test with the tool shape on a skin artifact under conditions equivalent to conditions of the first impact test. Optionally, the step of conducting an impact test with a tool shape on a skin artifact and a muscle artifact includes conducting a single impact test on the skin artifact attached on an outer surface of the muscle artifact.

[0019] The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings.

[0020] Brief Description of the Drawings

[0021] FIG. 1 shows a schematic diagram of an exemplary testing apparatus.

[0022] FIG. 2 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the RB family of rectangular cross section tools of 24 mm x 19 mm dimensions vs their fillet radii and 0.9 m / s impact speed.

[0023] FIG. 3 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the RB family of rectangular cross section tools of 24 mm x 19 mm dimensions vs their fillet radii and 0.9 m / s impact speed.

[0024] FIG. 4 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the RL family of rectangular cross section tools of 12 mm x 9.5 mm dimensions vs their fillet radii for 0.9 m / s impact speed.

[0025] FIG. 5 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the RL family of rectangular cross section tools of 12 mm x 9.5 mm dimensions vs their fillet radii for 0.9 m / s impact speed.

[0026] FIG. 6 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the CB family of cylindrical cross section tools of 20 mm Diameter vs their fillet radii for 0.9 m / s impact speed.

[0027] FIG. 7 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the CB family of cylindrical cross section tools of 20 mm Diameter vs their fillet radii for 0.9 m / s impact speed.

[0028] FIG. 8 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the CL family of cylindrical cross section tools of 10 mm Diameter vs their fillet radii for 0.9 m / s impact speed.

[0029] FIG. 9 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the CL family of cylindrical cross section tools of 10 mm Diameter vs their fillet radii for 0.9 m / s impact speed. FIG. 10 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the HB family of hexagonal cross section tools of 20 mm side to side vs their fillet radii for 0.9 m / s impact speed.

[0030] FIG. 11 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the HB family of hexagonal cross section tools of 20 mm side to side vs their fillet radii for 0.9 m / s impact speed.

[0031] FIG. 12 shows a graph of the maximum impact von Mises stress distributions of artifacts in ballistic gelatin for the HL family of hexagonal tools of 10 mm side to side vs their fillet radii for 0.9 m / s impact speed.

[0032] FIG. 13 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the HL family of hexagonal tools of 10 mm side to side vs their fillet radii for 0.9 m / s impact speed.

[0033] FIG. 14 shows a graph of the maximum impact von Mises stress distributions of artifacts in the ballistic gelatin for the CB family of cylindrical cross section tools of 20 mm diameter vs their fillet radii for 1 .6 m / s impact speed.

[0034] FIG. 15 shows a graph of the maximum impact von Mises stress distributions of artifacts in the skin for the CB family of cylindrical cross section tools of 20 mm diameter vs their fillet radii for 1 .6 m / s impact speed.

[0035] FIG. 16 shows a graph of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the CA family of cylindrical tools of 13 mm diameter vs their fillet radii for 1 .6 m / s impact speed.

[0036] FIG. 17 shows a graph of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the C30 family of cylindrical cross section tools of 30 mm diameter vs their fillet radii for 0.58 m / s impact speed.

[0037] FIG. 18 shows a graph of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the CB family of cylindrical tools of 20 mm diameter vs their fillet radii for 0.58 m / s impact speed.

[0038] Detailed Description

[0039] Conventionally the fillet radius of tools or assembly pins is selected arbitrarily or without rigorous regard for injury probability or severity. Presented herein is a new method for their selection using science-based rules. Our impact test results indicate that, under the same impact conditions, a small fillet radius selection, results in high impact surface damage, while a large fillet radius selection results in deep, bullet type, penetration damage. The preferred geometry choice, that our impact technique reveals, results in a balance between these two bad outcomes.

[0040] A persistent high rate of fatal accidents involving industrial robots motivates a desire to develop a simple impact testing instrument, human tissue-representing artifacts, and maximum deformation stress measures, following the impact of common shape manufacturing tools and assembly parts, on these artifacts. These stress measures are then used to rank the injury safety margin of these tools. A method for determining preferred designs for each tool shape studied are also presented, which minimizes the level of maximum stress, under the same impact testing conditions. Also, the preferred tool design rules follow a linear scale law of their impact surface dimensions, for different sizes of the same shape tools. The methodology developed can then be used to rank preferred geometry tools of different shapes and sizes according to their injury safety margin. This methodology of preferred geometry designs can be applied to other parts of robot arms, like elbows, wrists, etc.

[0041] Referring first to FIG. 1 , for dynamic impact testing, an exemplary tester is shown at 100. Alternatively, a commercial Kapuskasing Style Drop Impact Tester, potentially with minor modifications, may be used. This is a relatively inexpensive, simply designed, manually operated desktop impact testing machine, with a significant data collection and analysis capability. Various sensors may be added for the measurement of the impact force, the deformation of the impacted target and a high-speed camera used for the recording of the impact event. The Drop Impact Tester includes a horizontal metal base plate, the impact load mechanism supporting vertical beam mounted on the back of the base plate, an impact rod bracket dual bushing mechanism mounted on the supporting vertical beam, and an impact rod with safety pin height adjustment holes. The tester is a freefall, gravity-generated impact force, where the impact speed is proportional to the square root of the drop height and the impact kinetic energy is proportional to the product of the drop height with the drop mass weight. A simple way to vary the impact force is to have several weights mounted at the lower end of the impact rod. These metal blocks may also be used for mounting various impact sensors, like accelerometers, displacement sensors, and / or an impact force measurement load-cell mounted at the bottom surface of the metal block. The load-cell may also be used for the mounting of the impact tools.

[0042] Impact testing artifacts may consist of bio-simulant skin artifact 110 firmly attached to (preferably cylindrical) blocks of ballistic gelatin muscle artifact 120.

[0043] The bio-simulant skin artifact 110 may be made of semi-finished chrome tanned upholstery “crust” cowhide leather of 0.9 mm to 1 .1 mm nominal thickness, having tensile strength and elongation at breaking, comparable to human skin, used by forensic scientists, when assessing the injury potential of non-penetrating “less lethal” kinetic impact ammunition and relatively low energy ricochet fragments. Alternatively, platinum-cured silicone elastomer, such as Ecoflex 00-30, may be utilized, because it has a reliable performance between room temperature of 20 °C to human body temperature of 36 °C. In addition to this feature, it has close resemblance to the material properties of human skin. The skin artifact can vary as long as its materials properties align with those of the target human body region under the impact conditions and provide reliable performance across a wide temperature range.

[0044] The muscle artifact 120 may be a block of ballistic gelatin made of water solutions containing 10% to 20% mass of gelatin, which is considered to be a good human muscle tissue impact bio-simulant, with good translucency for impact damage recording. However, ballistic gelatine’s mechanical properties may be close to human muscle only at the ambient room temperature of 4°C and are highly sensitive to factors such as curing temperature, preparation procedure, and maturation time. To address the temperature limitation, 10% synthetic ballistic gelatine may be used as human bio-simulant for the specific impact conditions, especially unexpected human-robot contact situations. Unlike conventional ballistic gelatin, the new materials perform stably in temperatures ranging from 0°C to 38°C, eliminating the need for additional temperature control during testing.

[0045] In recent years an alternative to ballistic gelatin has emerged, called “Ballistic Plastic”, which does not require refrigeration for prolong preservation. It has been found that this alternative bio-simulant generates very similar results to ballistic gelatin, following impact tests.

[0046] During testing the artifact may be placed on a spring supported metal stage 130. The rectangular frame of this stage may enclose one or more (preferably several steel music wire compression coil) springs 140, which simulate the stiffness of the simulated body part internal organs. Varying the number and stiffness of the coil springs allows the simulation of different values of body part stiffness. The stage 130 may be slidably coupled to one or more (preferably four) motion control guides 150, that guide the stage to move in only one dimension. The one or more springs 140 are configured to resist motion of the stage 130 in this dimension.

[0047] The maximum deformation energy theory, also called the maximum distortion energy theory, is considered the best theory for the prediction of the failure under loading of nonlinear elastic, viscoelastic, or linear elastic behavior materials. It claims that the material fails when its deformation energy under loading reaches a critical value.

[0048] If we now define the von Mises stress SVM as where aXx, oyy, azzare tensile or compressive stresses and rxy, ryz, TZX, are shear stresses, of a small element of the material, like, for example, a FEM simulation element, inside the elastic material.

[0049] The deformation energy under loading dUdef of this small element is given by: where v is the Poison ratio, and E the Young’s modulus of elasticity of the material, and dV is the volume of the small element of the material under loading.

[0050] An important point to notice from the last equation is that the deformation energy under loading dUdef is proportional to the von Mises stress SVM- Based on that observation the material fails when the von Mises stress reaches a certain value, known as its yield strength. In the case of injuries to humans, this means that a high value impact von Mises maximum stress is undesirable, because it brings human artifact comparators closer to failure.

[0051] Unfortunately, the impact von Mises maximum stress cannot be measured directly but has to be calculated with Finite Element Analysis simulations of the impact event, based on information, like the impact kinetic energy, the impact speed, the description of the impact tool surface geometry and the material properties of our artifact skin (modeled as a higher density gelatin), ballistic gelatin and the stiffness of the artifact mounting platform. A large number of impact tests were conducted for three different impact speeds of 1 .6 m / s, 0.9 m / s and 0.58 m / s. Three different generic shapes of tools were used for these tests: rectangular, cylindrical, and hexagonal. The cross-section dimensions of the rectangular tools, here called RB, were 24 mm x 19 mm and the dimensions of the rectangular tools, here called RL, were 12 mm x 9.5 mm. The dimensions of the cylindrical tools, here called C30, were 30 mm diameter, the cylindrical tools, here called CB, were 20 mm diameter, the cylindrical tools, here called CA, were 13 mm diameter and the cylindrical tools, here called CL, were 10 mm diameter. The dimensions of the hexagonal tools, here called HB, were 20 mm side to side and the dimensions of the hexagonal tools, here called HL, were 10 mm side to side. Each of the above tool shapes and sizes formed a family of up to 11 tools of the same shape and size but different fillet radius. The fillet radii varied from 0, to 1 mm and then increments of 1 mm, with a possible maximum of 10 mm.

[0052] FIGs. 2 and 3 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the RB family of rectangular cross section tools vs their fillet radii and 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a 5.0 mm fillet radius for the ballistic gelatin and a 6 mm fillet radius for the skin of the artifact.

[0053] FIGs. 4 and 5 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the RL family of rectangular cross section tools vs their fillet radii for 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 2.5 mm for the ballistic gelatin and by a fillet radius of 2.5 mm for the skin of the artifact.

[0054] These results show that for a linear-dimensions-ratio of 2 between the two rectangular families of RB and RL tools, the preferred-fillet-radius ratio is 2.0 for ballistic gelatin and 2.4 for skin.

[0055] FIGs. 6 and 7 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the CB family of cylindrical cross section tools vs their fillet radii for 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 4 mm for the ballistic gelatin and by a fillet radius of 4 mm for the skin of the artifact. FIGs. 8 and 9 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the CL family of cylindrical cross section tools of 10 mm Diameter vs their fillet radii for 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 2 mm for the ballistic gelatin and by a fillet radius of 3 mm for the skin of the artifact.

[0056] These results show that for a linear-dimensions-ratio of 2 between the two cylindrical families of CB and CL tools, the preferred-fillet-radius ratio is 2.0 for ballistic gelatin and 1 .3 for skin.

[0057] FIGs. 10 and 11 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the HB family of hexagonal cross section tools of 20 mm side to side vs their fillet radii for 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 6 mm for the ballistic gelatin and by a fillet radius of 6 mm for the skin of the artifact.

[0058] FIGs. 12 and 13 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the HL family of hexagonal tools of 10 mm side to side vs their fillet radii for 0.9 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 3 mm for the ballistic gelatin and by a fillet radius of 3 mm for the skin of the artifact.

[0059] These results show that for a linear-dimensions-ratio of 2 between the two hexagonal families of HB and HL tools, the preferred-fillet-radius ratio is 2.0 for ballistic gelatin and 2.0 for skin.

[0060] FIGs. 14 and 15 show two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin, respectively) for the CB family of cylindrical cross section tools of 20 mm diameter vs their fillet radii for 1 .6 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 4.5 mm for the ballistic gelatin and by a fillet radius of 4.5 mm for the skin of the artifact.

[0061] FIG. 16 shows a graph of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the CA family of cylindrical tools of 13 mm diameter vs their fillet radii for 1 .6 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 3 mm for the ballistic gelatin and by a fillet radius of 3 mm for the skin of the artifact.

[0062] These results show that for a linear-dimensions-ratio of 1 .53 between the two cylindrical families of CB and CA tools, the preferred-fillet-radius ratio is 1 .53 for ballistic gelatin and 1 .53 for skin.

[0063] FIG. 17 shows two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the C30 family of cylindrical cross section tools of 30 mm diameter vs their fillet radii for 0.58 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 6 mm for the ballistic gelatin and by a fillet radius of 6 mm for the skin of the artifact.

[0064] FIG. 18 shows two graphs of the maximum impact von Mises stress distributions of artifacts (in ballistic gelatin and in the skin) for the CB family of cylindrical tools of 20 mm diameter vs their fillet radii for 0.58 m / s impact speed. It is apparent from these graphs that the minimum von Mises impact stress is accomplished by a fillet radius of 4 mm for the ballistic gelatin and by a fillet radius of 4 mm for the skin of the artifact.

[0065] These results show that for a linear-dimensions-ratio of 1 .5 between the two cylindrical families of C30 and CB tools, the preferred-fillet-radius ratio is 1 .5 for ballistic gelatin and 1 .5 for skin.

[0066] Table 1 , below, shows a summary of these results indicating that all of them reveal the existence of a preferred geometric shape of the tip of tools or assembly pins, used by industrial robots, which minimizes the maximum von Mises stress in the case of an impact with a viscoelastic material, and that this rule follows a linear cross section scale rule, with an average error of 0.07 (7%).

[0067] Table 1. Summary of Experimental Results

[0068]

[0069] These impact test results indicate that, under the same impact conditions, a small fillet radius selection, results in high impact surface damage, while a large fillet radius selection results in deep, bullet type, penetration damage. The preferred geometry choice, that our impact technique reveals, results in a balance between these two bad outcomes.

[0070] Therefore, herein disclosed is a method for designing robot tools and parts that includes the steps of determining the von Mises maximum impact stress as a function of the fillet radius of a family of robot tools of the same shape and size and selecting the one with the lowest von Mises maximum impact stress as a preferred geometry tool. Optionally, the steps of determining the von Mises maximum impact stress and selecting one with the lowest von Mises maximum impact stress include selecting a tool fillet radius from a look-up table.

[0071] Also disclosed herein is a method for predicting a preferred fillet radius tool including the steps of identifying a preferred geometry for a first tool shape, using a linear scale rule to predict a preferred fillet radius of a second tool based on the first tool shape.

[0072] Also disclosed herein is a method for measuring robot tools impact injury level risk using the steps of conducting an impact test with a tool shape on a muscle artifact and a skin artifact under the same conditions, calculating a von Mises maximum impact stress for each of the muscle equivalent and the skin equivalent, and evaluating injury risk based on the von Mises maximum impact stress. The processes described herein may be embodied in, and fully automated via, software code modules executed by a computing system that includes one or more general purpose computers or processors. The code modules may be stored in any type of non-transitory computer-readable medium or other computer storage device. Some or all the methods may alternatively be embodied in specialized computer hardware. In addition, the components referred to herein may be implemented in hardware, software, firmware, or a combination thereof.

[0073] Many other variations than those described herein will be apparent from this disclosure. For example, depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multithreaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines and / or computing systems that can function together.

[0074] Any logical blocks, modules, and algorithm elements described or used in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and elements have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure.

[0075] The various illustrative logical blocks and modules described or used in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a processing unit or processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor includes an FPGA or other programmable device that performs logic operations without processing computerexecutable instructions. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor may also include primarily analog components. For example, some or all of the signal processing algorithms described herein may be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.

[0076] The elements of a method, process, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module stored in one or more memory devices and executed by one or more processors, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of non- transitory computer-readable storage medium, media, or physical computer storage known in the art. An example storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The storage medium can be volatile or nonvolatile.

[0077] While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation. Embodiments herein can be used independently or can be combined.

[0078] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The ranges are continuous and thus contain every value and subset thereof in the range. Unless otherwise stated or contextually inapplicable, all percentages, when expressing a quantity, are weight percentages. The suffix (s) as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorants). Option, optional, or optionally means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. As used herein, combination is inclusive of blends, mixtures, alloys, reaction products, collection of elements, and the like.

[0079] As used herein, a combination thereof refers to a combination comprising at least one of the named constituents, components, compounds, or elements, optionally together with one or more of the same class of constituents, components, compounds, or elements.

[0080] All references are incorporated herein by reference.

[0081] The use of the terms “a,” “an,” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. It can further be noted that the terms first, second, primary, secondary, and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. For example, a first current could be termed a second current, and, similarly, a second current could be termed a first current, without departing from the scope of the various described embodiments. The first current and the second current are both currents, but they are not the same condition unless explicitly stated as such.

[0082] The modifier about used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). The conjunction or is used to link objects of a list or alternatives and is not disjunctive; rather the elements can be used separately or can be combined together under appropriate circumstances. Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e. , that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

Claims

Claims1. A method of designing robot tools and parts, the method comprising the steps of: determining a plurality of von Mises maximum impact stresses as a function of fillet radius of a family of robot tools of same shape and size; determining a lowest von Mises maximum impact stress from the plurality von Mises maximum impact stresses; and selecting a fillet radius for a robot tool based on the determined lowest von Mises maximum impact stress.

2. The method of claim 1 , wherein, the step of selecting a fillet radius for a robot tool includes selecting a tool fillet radius from a look-up table.

3. A method of predicting a preferred fillet radius tool, the method comprising the steps of: identifying a preferred geometry for a first tool shape; and predicting a preferred fillet radius of a second tool shape based on the first tool shape using a linear scale rule.

4. A method of measuring robot tools impact injury level risk, the method comprising the steps of: conducting an impact test with a tool shape on a skin artifact and a muscle artifact; calculating a von Mises maximum impact stress for each of the muscle artifact and skin artifact; and evaluating injury risk based on the von Mises maximum impact stresses.

5. The method of measuring robot tools impact injury level risk of claim 4, wherein the step of conducting an impact test with a tool shape on a skin artifact and a muscle artifact includes: conducting a first impact test with a tool shape on a muscle artifact; and conducting a second impact test with the tool shape on a skin artifact under conditions equivalent to conditions of the first impact test.

6. The method of measuring robot tools impact injury level risk of claim 4, wherein the step of conducting an impact test with a tool shape on a skin artifact and a muscle artifact includes: conducting a single impact test on the skin artifact attached on an outer surface of the muscle artifact.

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