FIELD

The invention relates to mechanisms emulating motions of animals, and, in particular, to a mechanism emulating neck movements of quadruped mammals.

BACKGROUND INFORMATION

There is a long history of human-made mechanisms trying to replicate motions of an animal. Such mechanisms may be used for educational, recreational, or other purposes. Emulation of movements by a mechanism can be useful when a living animal cannot be used or use of a living animal would be ineffective, e.g. in a long working process in which living animal would be exhausted or a process where an animal could be put in danger. Practical examples are film making, using fake animal in a performance, or using the mechanism in simulator. For example, a mechanism emulating motions of a horse may be used as a part of the horse-riding simulator.

While it may be desirable to produce as realistic motion as possible, replicating all features of motion of an animal with a mechanical structure may be a very challenging task (or may be impossible in practice]. Therefore, some types of movements are typically simplified or omitted altogether. For example, existing solutions that aim to imitate an animal motion often do not have a neck or head motion at all. Some of solutions have two degrees of freedom with complex drivetrains and a solid neck frame. However, the existing solutions typically do not produce motion that captures the movements of an animal in an authentic manner. Further, complex drivetrains may be more prone to a mechanical failure.

BRIEF DISCLOSURE

An object of the present disclosure is to provide a mechanism so as to alleviate the above disadvantages. The object of the disclosure is achieved by the mechanism, which is characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

A mechanism according to the present disclosure comprises a neck frame that is

RECTIFIED SHEET (RULE 91) ISA/EP configured to be connected [or integrally attached) to an external frame. The external frame may be in the form of a base frame emulating a body of an animal, for example. The neck frame may be in the form of a planar six-bar linkage. Proportions of link bars in the linkage may be determined based on the proportions of the animal. A joint in the middle portion of the neck frame effectively splits the neck frame into two sections. This approach allows neck to bend in the middle point which makes the motion of the neck frame more realistic. The planar six-bar linkage of the neck frame enables a complex motion that is restricted to a plane [i.e. the plane of the neck frame). During use, said plane is a vertical plane. In order to actuate the neck frame, it may be coupled with a first actuator. The first actuator may located on the external frame to which neck is attached. The first actuator provides the motion of the neck frame in the vertical plane, and thus, provides the mechanism its first degree of freedom [DOF). The mechanism may further comprise a spring or springs that provides gravity compensation for the first actuator. In addition to the neck frame, the mechanism may comprise a head frame. The head frame may be attached to the neck frame with spherical joint [or combination of revolution joints). To actuate the head frame, a second actuator may be located on the neck frame in order to rotate the head frame with respect the neck frame in the vertical plane, thereby providing flexion and extension movements of the head frame and a second degree of freedom for the mechanism. The second actuator may also be aided with spring providing gravity compensation. The mechanism may further comprise a third actuator which allows rotation in the horizontal plane, thereby providing the mechanism with rotation of the head frame, thereby serving as third degree of freedom. The third actuator may be located on the neck frame or on the head frame and is used to provide head motion in the horizontal plane.

The mechanism according to the present disclosure provides a realistic motion of a head and neck of a quadruped mammal while at the same time being robust. The mechanism can easily be utilized in large number of applications for educational, recreational or other purposes. In addition, with a spring or springs providing gravity compensation, the mechanism according to the present disclosure can be operated in an energy-efficient manner. Further, with the elastic material imitating skin elasticity, a more realistic emulation of the neck of an animal can be achieved.

RECTIFIED SHEET (RULE 91) ISA/EP BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figures la and lb show an example of a mechanism according to the present disclosure;

Figures 2shows examples of motion trajectories produced with a mechanism according to the present disclosure;

Figure 3 shows a simplified example of exemplary alternative positions of base joints;

Figure 4 shows an isometric diagram of a cover structure for a neck frame according to the present disclosure; and

Figure 5 shows proportion values relevant to a neck frame according to the present disclosure.

DETAILED DISCLOSURE

The present disclosure describes a mechanism emulating neck and head motion of a quadruped (i.e. four-footed) mammal. The mechanism may be used to imitate horse head and neck motion in a horse-riding simulator, for example.

A mechanism according to the present disclosure comprises a neck frame, a head frame, and actuators. The neck frame is split into two main parts that are connected via a joint. This approach allows neck to bend in the middle point which makes the motion of the neck frame more realistic. The neck frame forms a planar six-bar linkage. In the context of the present disclosure, the term “planar" in conjunction with the term "linkage" is intended to be understood to mean a linkage having a motion trajectory constricted to a plane. In the mechanism according to the present disclosure, the six-bar linkage may comprise a ternary link and four binary links. In the context of the present disclosure, the term "ternary link" refers to a part (e.g. beam, rod, or bar) of the linkage that has three separate connection

RECTIFIED SHEET (RULE 91) ISA/EP points, and the term "binary link" refers to a part of the linkage that has two separate connection points.

In the neck frame according to the present disclosure, the links may be connected to each other with five binary joints and one ternary joint. In the context of the present disclosure, the term "ternary joint" refers to a joint that connects three parts of the linkage to pivot about the same axis. In some embodiments, two coaxial binary joints act as a ternary joint. The term "binary joint” refers to a joint that connects two parts of the linkage. In the planar six-bar linkage of the neck frame according to the present disclosure, the six abovementioned joints may all be revolute joints. The revolute joints may all have parallel axes (that are perpendicular to the plane of the neck frame), thereby restricting the motion of the neck frame to the plane of the neck frame. In the neck frame, a first binary joint connects a first link bar to a base frame and a second binary joint connects the first link bar to a second link bar. The first and second link bar may be seen as the two main parts of the neck frame. Complex motion of these two parts on the vertical plane imitates motion of a mammal neck. To complete the linkage, a third binary joint (acting as a second base joint) connects a third link bar to the base frame and a ternary joint connects the third link bar to a fourth link bar and a fifth link bar. A fourth binary joint connects the fourth link bar to the first link bar, and a fifth binary joint connects the fifth link bar to the second link bar.

Figures la and lb show an example of a mechanism according to the present disclosure. Figure la show a sideview of the mechanism while Figure lb show top view of the portion of the mechanism with the head frame. In Figure la, five link bars LI to L5 are shown. The first link bar LI forms a ternary link while the other link bars L2 to L5 form binary links. The first link bar LI in Figure la is a straight beam with a first connection point at one end, a second connection point at the other end, and a third connection point therebetween. The second link bar L2 is also a straight beam with a first connection point at one end and a second connection point in its middle portion. The third link bar L3, the fourth link bar L4, and the fifth link bar L5 all have their first and second connection points at both ends of them. The neck frame may be attached to an external frame which may be a base frame emulating the shape of an animal body, for example. Connection points G1 and G2 of an external frame form as a stationary sixth link bar acting a

RECTIFIED SHEET (RULE 91) ISA/EP binary link. Figure 1 also shows five binary joints JI to J5 and a ternary joint J6. All six joints JI to J6 may be revolute joints. In Figure la, a first binary joint JI acts as a first base joint and connects the first connection point of the first link bar LI to a first connection point G1 of the external frame. The second binary joint J2 connects the second connection point of the first link bar LI to a first connection point of the second link bar L2. The third binary joint J 3 acts as a second base joint and connects a first connection point of the third link bar L3 to a second connection point G2 of the external frame. The ternary joint J6 connects a second connection point the third link bar L3, a first connection point of the fourth link bar L4, and a first connection point the fifth link bar L5 together. The fourth binary joint J4 connects a second connection point of the fourth link bar L4 to a third connection the first link bar LI. The third connection point of LI is positioned between the first and second connection point of LI. The fifth binary joint J5 connects a second connection point the fifth link bar L5 to a second connection point the second link bar L2.

In addition to the neck frame, a mechanism according to the present disclosure comprises a head frame. The second link bar may extend over the fifth joint thereby forming an arm, and the head frame may be connected to an end of the arm by a sixth joint. In Figures la and lb, a simplified representation of a head frame F2 is shown. The head frame has a tip F2-1 and a base F2-2, representing a nose and a base of the head of an animal, for example. The second link bar L2 is in the form of a straight beam that extends beyond the fifth joint J5 thereby form a straight arm. A seventh joint J7 connects the head frame F2 to the end of the arm. The seventh joint may be a spherical joint, for example, thereby allowing rotating motion in two perpendicular directions. Alternatively, a combination of two revolute joints may be used.

To actuate neck frame, the mechanism may comprise a first actuator directly or indirectly driving the main parts of the neck frame. In Figures la and lb, one embodiment of a first actuator Al according to the present disclosure is shown. In some embodiments, as in Figure la, the first actuator Al may comprise an electric motor and a timing belt transmission which provide revolute motion of third link bar L3 (i.e. the crankshaft). However, the mechanism according to the present disclosure is not limited only to such actuators. For example, a linear actuator may

RECTIFIED SHEET (RULE 91) ISA/EP also be used as the actuator Al.

The actuator Al in Figure la is not directly connected to the main parts, i.e. the first link bar LI and the second link bar L2. Instead, the first actuator is arranged to actuate the third link bar L3 so that the third link bar L3 acts as a crankshaft of a drivetrain in Figure la. This crankshaft L3 is connected to the fourth and fifth link bars L4 and L5 which act as two connection rods. Both connection rods L4 and L5 are attached to specific points of the main parts LI and L2 of the neck frame, thereby forming a quadrilateral shape with portions of the main parts and completing a drivetrain of the neck frame. All elements of the drivetrain are connected via revolute joints. Revolute motion of the crankshaft L3 makes the first link bar LI of the neck frame to rotate in the vertical plane of the neck frame and the second link bar L3 to make a complex motion in the same plane. In this context, the term "revolute motion" means back-and-forth rotation of the crankshaft L3 about the axis of the third binary joint J3.

In addition to the first actuator, the mechanism according to the present disclosure may further comprise a second and a third actuator. The second actuator may be arranged to provide flexion and extension motions of the head frame, while the third actuator may provide rotation of the head frame. Figure la shows a second actuator A2 connected between the head frame and the arm of the neck frame. Figure lb shows a third actuator A3 connected between the head frame and the arm of the neck frame.

In order to reduce workload of the actuators, the mechanism may be provided with a spring or springs that reduce gravitational load on the first actuator and the second actuator. For example, the mechanism may be provided with a first spring that reduces the gravitational load of the first actuator. In addition, or alternatively, the mechanism may comprise a second spring arranged between the arm of the neck frame and the base of the head frame, thereby reducing the gravitational load of the second actuator. The springs can be located at almost any point of the mechanism, and different spring types may be used. The location and type of a spring affect its mechanical design and required stiffness coefficient. One or more springs are preferably arranged to exert force on link bars LI or L3 (or both). In this manner, their stiffness coefficients can be maintained at manageably low level.

RECTIFIED SHEET (RULE 91) ISA/EP The springs may be tension or compression springs, for example. In Figure la, a first spring in the form of a compression spring SI acts on the third link bar L3 (which acts as the crank shaft). Alternatively, torsion springs may be arranged on joint JI or J3 or both. Figure la also shows a second spring in the form of a tension spring is arranged between the second link bar L2 and the base F2-2 of the head frame.

With the above-discussed combination of a neck frame, a head frame and actuators, a realistic emulation of neck movements of an animal can be produced. Figure 2 shows an example of the produced motion trajectories of an animal. The animal in question in Figure 2is a horse. Figure 2 shows some specific points of interest for motion analysis. In Figure 2, various points of the neck frame and the head are shown superimposed on top of a head and a neck of a horse (visualised in a dashed line). Figure 2 shows the position of the first joint JI and trajectories of the second joint J2, the seventh joint J7 and the tip F2-1 of the head frame. The seventh joint J7 corresponds with the joint between the spine and the base of skull of the animal or, i.e. the poll of a horse in Figure 2. The tip F2-1 of the head frame corresponds with the nose of the animal, i.e. the muzzle of a horse in Figure 2. The second joint J2 corresponds the upper neck of the of the animal, and the position of the first joint JI represents a centre point between the shoulders of the animal. The poll and the muzzle make reciprocating (i.e. back-and-forth) motions in the plane of the neck frame. As shown in Figure 2, the poll may move practically along a backward- slanted line (i.e. a line that is at an acute angle A with respect to the horizontal plane, the acute angle A opening towards the back of the horse). In contrast, the motion of the muzzle may be on a forward-slanted line (i.e. an acute angle B opening towards the front of the horse). As a result, the line of the reciprocating motion of the poll may at an acute angle C with line of the reciprocating motion of the muzzle. In more specific terms, the angle between the lines of the motions of the poll and the muzzle may be between 60 to 80 degrees, for example.

The neck motions follow a repeating pattern that maps to a gait pattern of limb movements of an animal. The same cycle of neck movements repeats itself at each cycle of the limb movements of the gait pattern. Thus, it is sufficient to have parameters for only one cycle of neck motions. Once one cycle is completed, the same cycle may be repeated from the start. To achieve a repeating pattern, the

RECTIFIED SHEET (RULE 91) ISA/EP actuators may have to have the same cycle length. In other words, they may operate in synchrony. In order to maintain synchrony, itmay be desirable to be able to keep track of the orientation/position of the actuators. For this purpose, the actuators may all be provided with position/orientation encoders that provide feedback on the actual position/orientation of the actuator. The position/orientation encoders may be integrated to the actuators.

To produce desired motions with a mechanism according to the present disclosure, the mechanism may further comprise a control system configured to control the actuators to actuate in synchrony. The control system may be in the form of a PLC (programmable logic controller), for example. The control system may comprise a computing device coupled with memory, outputs for controlling the actuators, and inputs for receiving the feedback information from the encoders. With the control system, the mechanism can replicate characteristics of different gaits of the same animal. For example, if the mechanism emulates neck movements of a horse, itmay emulate neck motion during walk, trot, canter, and gallop of a horse.

A desired gait can be provided by coordinated operation of two of the actuators: the first actuator (actuating the neck frame) and the second actuator (causing the flexion and extension movements). Different gaits may be defined based on the following parameters: motion amplitude, oscillation frequency, and initial position/orientation with respect to which oscillations occur. Each gait may have a different motion amplitude and initial orientation for each actuator. However, while the head frame and the neck frame may have their own initial positions/orientations, amplitudes, they oscillate with the same frequency. In other words, the actuators have the same cycle frequency but may have different amplitudes and phase shifts. The parameters (cycle frequency, phase shift, amplitude) may be predefined in the memory of the control system for each actuator for each gait. When user chooses one of the predefined gaits, the control system may control the actuators to orient head frame and neck frame in a certain position/orientation with respect to each other and then begin oscillations at the predefined amplitude and frequency.

While the mechanism according to the present disclosure has been discussed mostly in relation to the embodiment described in Figures la and lb, the

RECTIFIED SHEET (RULE 91) ISA/EP mechanism is not limited to said implementation. For example, while the above paragraphs discuss the mechanism in relation to embodiments where the third link bar acts as crank, the first link bar may be used as the crank instead. In such embodiments, the first actuator is attached directly to the first link bar. However, embodiments with the third link bar as the crank may be preferred as such arrangement may be more efficient. Further, the location of the base joints (and, therefore, the location of the connection points of the external frame] are not limited to those positions of joints JI and J3 shown in Figure la. The base joints can be relocated with respect to each other, and their relative positioning be determined based on the application (i.e. physical requirements of the implementation of the mechanism). Figure 3 shows a simplified example of exemplary alternative positions of base joints (i.e. the first joint JI and the third joint J3). In Figure 3, three alternative positions J3-1, J3-2 and J3-3 ofthe third joint J3 are shown Alternative positions may require changing proportions of bars, but the mechanism still will be able to reproduce the desired trajectory. For example, Figures la and 3 show an angled beam as the third link bar L3. In the embodiment shown in Figures la and 3, the third link bar L3 is angled to accommodate the gravity-compensating spring SI. However, the shape of the link bar itself does not defined trajectory, whereas distance between joints does. Therefore, the link bars in the neck frame of a mechanism according to the present disclosure may have different shapes that those presented in the drawings. For example, if no gravitycompensating spring is being used, the link bar L3 may be a straight beam. Alternatively, the spring may be positioned elsewhere thus requiring a different shape of for the third link bar. The mechanism according to the present disclosure has been mostly discussed in relation to embodiments where the head frame is attached to the neck frame via a spherical joint (allowing two degrees of freedom) and actuated by two actuators. However, the mechanism may also be implemented in a simplified form comprising a planar head j oint and only one actuator actuating the headframe and another actuator actuating the neck frame.

In the mechanism according to the present disclosure, the neck frame may be provided with a cover structure in order to achieve a more realistic emulation of the neck of an animal. For example, the mechanism may comprise hoops arranged around the neck frame, and elastic cover may be stretched on top of the hoops to imitate skin of an animal. The elastic cover may be in the form of a tube made of a

RECTIFIED SHEET (RULE 91) ISA/EP sheet of elastic material (such as rubber]. In one embodiment, three hoops are used. Figure 4 shows an isometric diagram of such an embodiment. In Figure 4, three hoops Hl, H2 and H3 are arranged around a neck frame according to the present disclosure. Only the first link bar LI and the second link bar L2 of the neck frame are shown in Figure 4. The first hoop Hl may attached to the external frame (indicated by the three slashes in at the periphery of the hoop). The second hoop H2 may attached to the first link bar LI at the second joint J2, and the third hoop H3 is attached to the head frame F2. In order to achieve natural-looking bending of the neck structure, the second hoop H2 may be attached to the first link bar LI (or to the second link bar L2] with a revolute joint (that is coaxial to the second joint J2 of the neck frame], thereby allowing the second hoop H2 to rotate freely with respect to the neck frame. In some embodiments, the elastic cover may be implemented with one elastic material that forms the surface of the cover. In other embodiments, an elastic material is used as a supportive overlay, and one or more additional materials are arranged on top of this supportive overlay. These additional materials may be used provide better imitation of the appearance and texture of the skin of the animal, for example. The number of hoops is not limited to three in the mechanism according to the present disclosure. Further, the mechanism may also be implemented without hoops and elastic material. For example, in some embodiments, the neck frame maybe covered with pieces of rigid cover instead of a stretchy material

As described above, the mechanism according to the present disclosure may be used for emulating neck movements of different species of animals. For example, in some embodiments, the mechanism is used to emulate movements of a horse. The proportions of the link bars of a neck frame according to the present disclosure may be adapted based on the proportions of the animal. Specific points of the mechanism can be mapped to specific anatomical features of the animal. For example, as shown in Figure 2, the position of the tip of the head frame may represent the position of the nose of the animal. The position of the seventh joint J7 may representthe joint between the spine and the base of the skull of the animal, the position of the second joint J2 may represent the position of the upper neck, and the position of the first joint JI may represent the centre point between the shoulders of the animal. Figure 5 shows proportion values relevant to a neck frame according to the present disclosure. The values Ll-1 and Ll-2 represent

RECTIFIED SHEET (RULE 91) ISA/EP proportions of the first link bar (LI in Figure la]. Ll-1 is the distance between the first and second connection point of the first link bar (i.e. the distance between the first join JI and second joint J2 in Figure la]. Ll-2 is the distance between the second and third connection point (i.e. the distance between the second joint J2 and fourth joint J4 in Figure la]. The values L2-1 and L2-2 represent proportions of the second link bar (L2 in Figure la]. L2-1 is the distance between the first connection point and the end of the arm of the second link bar L2 (i.e. the distance between the second joint J2 and the seventh joint J7 in Figure la]. L2-2 is the distance between the first and second connection point of L2 (i.e. the distance between the second joint J2 and fifth joint J5 in Figure la]. The values L3, L4, and L5 represent proportions of the third link bar (L3 in Figure la, i.e. the distance between joints J3 and J6], the fourth link bar (L4 in Figure la, i.e. the distance between joints J4 and J6 ], and the fifth link bar (L5 in Figure la, , i.e. the distance between joints J5 and J6], respectively.

Further, the mechanism can even be used to emulate neck movements different breeds within an animal species. For example, proportions of linkage bars for a mechanism simulating neck movements of a Brazilian Sport Horse are shown in Table I. The columns represent the beam dimensions presented in Figure 4.

Table 1. Proportions of horse breed "Brazilian Sport Horse" (dimensions in arbitrary units]

It is obvious to a person skilled in the art that the neck frame and the mechanism can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

RECTIFIED SHEET (RULE 91) ISA/EP