APPARATUS FOR GENERATING INFORMATION WHICH DEFINES IMAGINARY SUR FACES

Abstract: Primary transducers (3 to 8) yieldably support a spacial probe (2) in position relative to an imaginary surface defined by information stored in a computer memory system (1). A load cell (10) detects the magnitude and direction of forces applied to the probe (2) by an operator and control means (3) responsive to the position of the probe (2) relative to a first imaginary surface and to the magnitude and direction of the forces detected by the load cell (10) generate a control signal which is transmitted to the primary transducers (3 to 8) to position the probe (2). The control means (9) are operable to vary the resistance to movement to the probe (2) when the probe (2) is moving on one side of the first imaginary surface, along the first imaginary surface, or on the other side of the first imaginary surface. The control means are also operable, in response to movement along a second imaginary surface, displaced from the first imaginary surface, to alter the information stored in the computer memory system (1) so that this information defines the second imaginary surface. Alternatively, the control means (9) are operable to change the information stored by the computer memory system (1) to define a second imaginary surface which is displaced, by a fixed amount or by an amount dependent on the force exerted on the probe normal to the first imaginary surface, from that part of the first imaginary surface along which the probe (2) is moved.

Description: Apparatus for Generating Information which defines Imaginary Surfaces Technical Field The invention relates to apparatus for generating information which defines imaginary surfaces for producing articles having physically advantageous and/or aesthetically pleasing shapes. The invention is therefore relevant to the design and manufacture of complex surfaces, both styled and functional, such as car bodies, turbine blades, air ducts, covers, cowlings, fairings, shaped brackets, chassis, links and other mechanical components. Background Art Traditional techniques of generating shapes include the use of mock-ups made from easily shaped material such as plaster, wood and plastic. These mock-ups are carved and shaped by hand to produce models or patterns which are measured and drawn so as to enable toolmakers to make manufacturing tools for producing articles of the required shape. In an alternative method involving computer-aided design and computer- aided manufacture, shape data are supplied to a computer which is programmed to interpret sparse data to generate a record defining the entire surface. The computer may be programmed to then produce instructions for a machine tool to manufacture the parts or to manufacture tooling for production of the parts. The shape data supplied to the computer may relate to control points which dictate the shape of limited areas of the surface. The complete surface may be defined by a number of these limited areas with their accompany¬ ing control points. The shape data or control point positions supplied to the computer may be entered as explicit co-ordinates by means of a keyboard, or from a storage medium such as a magnetic card or tape. Shape data relating to planar shapes and cross-sections may also be dictated by a digitiser device such as a stylus or light pen which is moved in a plane and has its position detected by electronic or mechanical and electronic means. Alternatively, the data may relate to shapes built up by the addition or subtraction of standard volumes such as cubes and cylinders. To facilitate OMPI these processes, the shapes and sections may be displayed by any suitable image generation technique. In carrying out this method involving computer-aided design and computer-aided manufacture, it is known to provide apparatus, for generating information which defines a surface, comprising a computer memory system capable of storing information defining a first imaginary surface; a probe; primary transducer means for generating a first signal dependent on the deviation of the probe from a datum position; and control means operable in response to the first signal to vary the information stored by the computer memory system so that this information defines a second imaginary surface which differs from the first imaginary surface by an amount commensurate with the deviation of the probe from the datum position. In apparatus such as this, the probe may be in the form of a stylus which is movable across a plane from a datum position defined by an imaginary line representing a planar shape or cross-section. In this case, a signal from the control means, indicative of the deviation of the stylus from the imaginary line, can be used to provide a visual display of a marker which moves, relative to a visible line representing the planar shape or cross-section, in the same way as the stylus moves relative to the imaginary surface. As an alternative, the probe may be in the form of a light pen which is movable across a planar screen on which a visible line representing the datum position is displayed. In both cases, the control means are operable in response to the first signal, from the transducer means, to vary the information stored by the computer memory system so that the updated information defines a second imaginary surface, this second imaginary surface is displayed as a new visible line passing through the marker or through the tip of the light pen and this new visible line replaces the original line representing the first imaginary surface. While this apparatus is satisfactory for varying planar surfaces and cross-sections of articles having three-dinensional surfaces, difficulty is encountered in the use of this apparatus for generating three-dimensional surfaces because of the difficulty in visualising OMPl the shape of a three-dimensional surface by viewing a series of cross-sections of this surface and because of the difficulty in building up a smooth surface from a number of arbitrary areas or lines which are varied independently. Disclosure of the Invention The purpose of the present invention is to provide means whereby the difficulty encountered with this known form of apparatus is reduced. This is achieved by providing the probe in the form of a spacial probe having six degrees of freedom of movement relative to a datum having the shape of the first imaginary surface; by providing secondary transducer means for generating a second signal dependent on the direction and magnitude of forces applied to the special probe; by providing the control means in a form operable, in response to the first and second signals, to generate a third signal; and by providing the primary transducer means in a form operable to position the spacial probe in accordance with the third signal from the control means. Thus, according to the invention, there is provided apparatus, for generating information which defines a surface, comprising a computer memory system capable of storing information defining a first imaginary surface; a special probe having six degrees of freedom of movement relative to a datum having the shape of the first imaginary surface; primary transducer means for generating a first signal dependent on the deviation of the probe from a datum position; secondary transducer means for generating a second signal dependent on the direction and magnitude of forces applied to the spacial probe by an operator; and control means which axe operable, in response to the first signal, to vary the information stored by the computer memory system so that this information defines a second imaginary surface which differs frcπi the first imaginary surface ' of the probe from the datum position by an amount commensurate with the deviation t and, in response to the first and second signals, to generate a third signal; the primary transducer means being - A - operable to position the spacial probe in accordance with the third signal. The primary transducer means thus comprise apparatus for producing a measurement signal from a displacement and for changing a signal to a displacement and the secondary transducer means comprise appar¬ atus for producing a measurement signal from a force. With apparatus such as this, it is possible to store information relating to a first imaginary surface in a computer memory system by conventional means, such as a keyboard, or by electromagnet tapes or discs, or simply by moving the spacial probe so as to trace out the first imaginary surface. This information can then be changed by moving the spacial probe so that, where required, the probe deviates from the first imaginary surface. As the third signal generated by the control means and, therefore, the position of the probe vary in accordance with the magnitude and direction of the force applied to the probe by an operator and also in accordance with the position of the probe relative to the datum having the shape of the first imaginary surface, the resistance to movement of the probe varies and so the operator -- s given the sensation of being able to feel the first imaginary surface. This enhances the operator's ability to visualise the first imaginary surface and to change the first imaginary surface to the second imaginary surface in a controlled manner. In particular, the primary transducer means may move the probe so that there is a first resistance to movement when the probe is moved on one side of the first imaginary surface, a second resist¬ ance to movement when the probe is moved along the first imaginary surface, and a third resistance to movement when the probe is moved on the other side of the first imaginary surface. The first resist- ance to movement can be uniform so that the probe * can be moved in direct response to the forces applied to the probe by the operator. Alternatively, resistance to upward and downward movements may be varied in accordance with a weight assigned to the probe whereas resistance to horizontal movement remains constant at a level consist- ent with the inertia of a probe having the assigned weight. The control means may be such that this assigned weight can be varied so that the probe is assigned the weight of different surface working tools. The second resistance may also be uniform or, alternatively, may vary in accordance with the force exerted by an operator on the probe normal to the first imaginary surface so that this resistance provides the sensation of friction, and the control means may be operable, on movement of the probe along the first imaginary surface, to vary the information stored by the computer memory system so that this information defines a second imaginary surface which is displaced from that part of the first imaginary surface along which the probe is moved by a fixed amount or by an amount dependent on the force exerted on the probe normal to the first imaginary surface. The control means are preferably such that the second resistance and/or the amount by which the second imaginary surface is displaced from the first imaginary surface can be adjusted. By this means, it is possible to provide the probe with the feel of different types of tool or appliance for removing or building up .thg surface of a body or to provide the feel of removing layers of different hardness or depositing layers of different viscosity. The control means may also be such that the third resistance varies in accordance with the deviation of the probe from the first imaginary surface and/or in accordance with the direction of movement of the probe so that the probe can be given the feel of different cutting tools which are used to penetrate surfaces and to provide the feel of different material worked upon by such tools. One example of the interaction between apparatus according to the invention and a designer using the apparatus is the provision of a new smoothly shaped end on a housing for an item of domestic equipment where the housing has already been designed using computer aided design techniques, but the final styling has not yet been done. OMPI The designer sits at a workstation. This consists of a spacial probe, a display unit, keyboard, and supporting computers and memory with programs. He calls up the housing by entering the appropriate commands on the keyboard and shows a picture of the housing on the display unit. He manipulates the size and position of the housing on the screen to obtain a convenient working view. This view may be shown by either a shaded picture or by a number of lines drawn at equal intervals on the surface of the housing. The designer then, using the keyboard commands, selects a 'hardness' for the imaginary material of the imaginary housing. He then grasps the handle of the spacial probe and activates it, choosing initially to activate it, for example as a coarse file. The designer, holding the handle of the spacial probe, moves it feeling the "weight" of the file and, as he moves it, a line segment appears on the display screen representing the file and its position relative to the housing. He continues moving the "file" until he feels a distinct change in the "weight" of the file (spacial probe handle). This change in "weight" occurs when the file is resting against the housing (although neither the file nor the housing physically exist but are held in the computer memories as data). The designer can lightly move the probe handle over the housing or increase the force exerted and again move the handle. With low forces exerted using a file, the surface profile vαll not be changed by much and there will be little, if any, change to the image on the display. With increased force more "material" would be removed and greater changes to the shape would be seen on the display. This simulates the operation of a file in real life. After the initial roughing out of the shape, the designer can, using keyboard commands, change the file for a finer file, and make the material of the housing effectively harder so that he may make smaller adjustments to the surface profile with each motion to smooth it. The design may, of course, rotate the image on the display and the effective angle of the work piece whilst he is shaping it, through say keyboard commands, and can correct any mistakes he thinks he has made by applying extra material to the surface as with a "negative file". There would be available a range of standard tools, but he could specify his own if he needed to. These could be added to his set and held in the computer memory ready for use on a later occasion. When the designer is satisfied with the shape, he can instruct the computer to produce commands for numerically controlled machine tools to manufacture a housing. Brief Description of the Drawings Figure 1 is a schematic arrangement of apparatus, for generating information which defines imaginary surfaces, in accordance with the invention; , Figure 2 is a schematic view of a first form of support means for a probe suitable for use in the apparatus illustrated in Figure 1; Figure 3 is an elevational view of a second form of support means for a probe suitable for use in the apparatus illustrated in Figure 1; and Figure 4 is a perspective view of apparatus according to the invention in which a probe is mounted on support means of the second form, shown in Figure 3. Modes of Carrying-Out the Invention As shown in Figure 1 the apparatus comprises a computer memory system 1, a spacial probe 2 and control means 9. Information in the form of shape data for a first imaginary surface are fed from a keyboard 11 or another source to the control means 9 through lines 12. A suitable signal, representative of this information, is generated in the control means 9 and transferred to the memory system 1 through lines 13. When required, this information is transferred from the memory system 1 to the control means 9 through lines 14. A suitable signal, capable of controlling the spacial probe 2 is passed to the spacial probe 2 through lines 15. The control means 9 are such that the input from the keyboard 11, through lines 12, may be replaced with an input through the lines 15 from the spacial probe 2 so that the special probe 2 may be used in the generation of information stored in the memory system 1. In addition to lines 15, further lines 16 extend from the spacial probe 2 to the control means 9 for the purpose of transmitting to the control means 9 signals dependent on the loading applied to the spacial probe 2 and on the position of the spacial probe 2 relative to a datum. The first imaginary surface is displayed by means of an image generator 17 connected to the processing apparatus through lines- 18. As shown in Figure 2, the probe 2 is movable by a first primary transducer 3 incorporating an electric motor driven screw assembly, attached to an arm 19 carrying the probe 2 and a base 20 carrying a bracket 21 to which the arm 19 is connected for pivotal movement about a horizontal axis 22. The base 20 is rotatable about a further horizontal axis 23 lying in a plane perpendicular to the axis 22 by means of a second primary transducer 4, incorporating an electric motor and gear drive. The base 20 is supported on a sleeve 24 which is non-rotatably supported on a vertical post 25 which is rotatable about its own axis 26 by means of a third primary transducer 5 Incorporating another electric motor and gear drive. The post 25 and electric motor 5 are supported on a saddle 27 which also supports a fourth primary transducer 6, incorporating an electric motor driven winch connected to a hoisting wire 28 which is trained over a pulley 29 at the head of the post 25 and connected to the sleeve 24 so as to move the sleeve 24 up and down the post 25. The saddle 27 is provided with roller supports 30 for sliding movement along an elongate horizontal cross-member 31 by means of a fifth primary transducer 7 incorporating an electric motor driven winch, connected to a traction wire 32 trained around a pulley 33 mounted on the cross-member 31. Finally, the cross-member 31 is provided with roller supports 34 for movement along horizontal rails 35 extending perpendicular to the cross-member 31 by means of a sixth primary transducer 8 incorporating an electric motor driven winch and traction wire 36 trained around a pulley 37 which is fixed relative to the rails 35. The primary transducer means ' 3 to 8 generate a first signal dependent on the deviation of the probe 2 from the first imaginary surface and pass this first signal to the control means 9 (Figure 1) via lines 15. As shown, the probe 2 is in the form of a handle which can be grasped by an operator and moved with six degrees of freedom of movement. The force applied to the probe 2, by the operator, is detected by secondary transducer means in the form of a strain-gauge load- cell 10 to generate a second signal which is dependent on the direction and magnitude of the forces applied to the probe 2. This signal is passed via lines 16 (Figure 1) to the control means 9 (Figure 1). The control means 9 then generate a third signal in response to the first and second signals and pass this third signal, via lines 15, to the primary transducer means 3 to 8 to position the probe 2. In the alternative form of support means for the probe 2 shown in Figure 3, a base 38 supports a post 39 which is rotatable about its vertical axis 40. A first link 41 is pivotally connected to the post 39 for rotational movement about a horizontal axis 42, a second link 43 is rotatable about its longitudinal axis 44 and pivotally connected to the first link 41 for rotational movement about its longitudinal axis 47 and pivotally connected to the second link 43 for rotational movement about a horizontal axis 48. The spacial probe 2 is in the form of a handle which is attached to the free end of arm 46 and capable of six degrees of freedom of movement. Primary transducer means (not shown) incorporating electrical, hydraulic or pneumatic motors are connected to a power supply through lines 49 and driven in accordance with a third signal transmitted from the control means 9 (Figure 1) through lines 15. As in the form of support means shown in Figure 2, resistance to movement of the probe 2 is measured by secondary transducer means in the form of a load cell 10 and a second signal commensurate with this resistance is transferred to the control means 9 through lines 16. As shown in Figure 4, a probe 2 is mounted on support means similar to those described with reference to Figure 3. The support means are mounted on control means 9 and the control means 9, keyboard 11 and visual display unit 17 are mounted on a desk 50 incorporating a microcomputer 51 incorporating the memory system 1 (Figure 1). Typically, the top of the post 39 is about 35 cm. above the top of the desk 50 and the first and second links 41 and 43 are about 30 cm. and 28 cm., respectively. Associated with each pivot and axis 40, 42, 44, 45, 47 and -48 (Figure 3) is a primary transducer (not shown) incorporating an electric motor and gearbox. Coupled to this is a potentiometric device to provide a signal giving the rotation at each axis. There are six microprocessor-based control loops, one for each primary trans- , ducer. These are conventional position servo loops. There are appropriate power supplies and switching circuits. The positional signal for each of the six servo loops is supplied by a further microprocessor (the position controller). This latter processor is capable of resolving a signal giving a required position, x,y,z, and rotation, p,q,r, for the probe 2, into the individual positions required for each primary transducer. The computer memory system 1 holds a description of the surface being worked on in the form of an array or table of spot heights O with, say 1000 rows and 1000 columns of heights. The shape of the tool being used is held in a similar way although, of course, its size is much smaller. .Alternatively, parametric descriptions of the surface and tool shapes may be used. The apparatus works on a cyclic basis, say 4000 cycles per second. At the start of each cycle the microcomputer 5 requests the current values of x,y,z,p,q,r, for the probe 2 from the position controller microprocessor. It uses this position information to work out the penetration of the tool into the surface and, from a knowledge of the previous values of x,y,z,p,q,r, the direction and speed of motion. The value of the forces exerted on the probe 2 by the operator are read in by the microprocessor. The forces the material exert on the tool may be worked out from the penetration and speed of tool motion and from the material hardness figure (this can be' an arbitrary multiplying factor which the operator can change). Thus the microcomputer 51 has a knowledge of the forces exerted on the probe 2 by the operator and on the probe 2 by the surface. Assuming an inertia figure (again an arbitrary inertia which may be modified by the operator to suit his requirements) the microcomputer 51 can work out the resultant accelerations in each of the six degrees of freedom and thus, by a knowledge of the velocity and position of the probe 2, it can work out a required new position at the end of that time interval. • These new values of x,y,z,p,q,r, are then sent to the position control microprocessor which resolves the positions and sends the position requirements to each of the six individual servo control loops. Since the cycle is very fast the motion of the probe feels smooth. C FI

Claims: - 12 - Claims 1. Apparatus, for generating information which defines a surface, comprising: a computer memory system (1) capable of storing information defining a first imaginary surface; a probe (2); primary transducer means (3 to 8) for generating a first signal dependent on the deviation of the probe (2) from a datum position; and control means (9) operable in response to the first signal to vary the information stored by the computer memory system (1) so that this information defines a second imaginary surface which differs from the first imaginary surface by an amount commensurate with the deviation of the probe (2) from the datum position; characterised in that: the probe (2) is a spacial probe having six degrees of freedom of movement relative to a datum having the shape of the first imaginary surface; secondary transducer means (10) are provided for generating a second signal dependent on the direction and magnitude of forces applied to the spacial probe (2); the control means (9) are operable, in response to the first and second signals, to generate a third signal; and the primary transducer means (3 to 8) are operable to position the spacial probe (2) in accordance with the third signal from the control means (9). O H 2. Apparatus according to Claim 1 , in which the control means (9) are operable to generate a third signal which causes the primary transducer means (3 to 8) to move the probe (2) so that there is a first resistance to ove- r ent when probe (2) is moved on one side of the first imaginary surface, a second resistance to movement when the probe (2) is moved along the first imaginary surface, and a third resistance to movement when the probe (2) is - moved on the other side of the first imaginary surface. 0 3- Apparatus, according to Claim 2, in which the first resistance to movement is uniform so that the primary transducer means (3 to 8) move the probe (2) in direct response to the forces applied to the probe (2). 4- Apparatus, according to Claim 2 or Claim 3 > in 5 which the second resistance is uniform and the control means (9) are operable, on movement of the probe (2) along the first imaginary surface, to vary the information stored by the computer memory system (1) so that this information defines a second imaginary surface which is 0 displaced from that part of the first imaginary surface along which the probe (2) is moved by a fixed amount or by an amount dependent on the force exerted on the probe normal to the first imaginary surface. 5. Apparatus, according to Claim 4, in which the 5 control means (9) can be adjustably set to provide the second resistance and/or the amount at different levels. 6. Apparatus, according to Claim 3 or Claim 5, in which the third resistance varies in accordance with the deviation of the probe from the first imaginary surface. 0 7 * Appartus, according to Claim 4, in which the third resistance varies in accordance with the deviation of the probe from the first imaginary surface. 8. Apparatus, according to Claim 3, Claim 5 or Claim 6, in which the third resistance varies in accordance with the direction of movement of the probe (2). 9- Apparatus, according to Claim 4, in which the third resistance varies in accordance with the direction of movement of the probe (2). -agtTEE OM

Inventors: CROUCH JEAN ELIZABETH, CROUCH STEPHEN JOHN, CROUCH, JEAN, ELIZABETH, CROUCH, STEPHEN, JOHN
Applicants: CROUCH JEAN ELIZABETH, CROUCH STEPHEN JOHN, CROUCH, JEAN, ELIZABETH, CROUCH, STEPHEN, JOHN
Application year: 1982
Main classification: G05B19
IPC codes: B25J9, G05B19, G06F3