NL2035535B1 - Actuator device comprising a driving member that is swivable around a first center of rotation, and a driven member that is swivable around a second center of rotation - Google Patents

Abstract

Actuator device (1) comprising a driving member (2) that is motor (3) driven and swivable around a first center of rotation (4), and a driven member (5) that is swivable around a second center of rotation (6), wherein the first center of rotation (4) and the second center of rotation (6) are distant from each other, and the driving member (2) connects via a connecting element (7) to at least one elastically resilient element (8, 9), wherein on their end or ends distant from the driving member (2) said elastically resilient element or elements (8, 9) is/are connected to a distant part or parts (5’, 5”) of the driven member (5).

Description

Actuator device comprising a driving member that is swivable around a first center of rotation, and a driven member that is swivable around a second center of rotation

The invention relates to an actuator device comprising a driving member that is motor driven and swivable around a first center of rotation, and a driven member which connects to the driving member, which driven member is swivable around a second center of rotation.

Such an actuator device can be embodied in a bicycle simulator, although also other applications are feasible.

Examples of other applications are robotic exoprostheses, industrial robots, or surgical devices. The invention is however best explained with reference to a bicycle simulator, but is evidently not restricted thereto.

A human rider can sit on the bicycle simulator and lean sideways like on a normal bike. The gravitational moment acting on the simulated bicycle and the rider can be quite large, for a heavy person up to 500 Nm in a range of +/- 20 degrees. This is a large moment, and finding a suitable motor to compensate this moment while staying within limited requirements for power consumption and safety is challenging.

The above challenge relates to a more general problem in haptic devices wherein electric motors are used, because electric motors generally excel at achieving high speeds (more than needed for these application), but not high torques. So, using electrical motors to actuate haptic devices often creates the challenge of generating sufficient torque.

This challenge is usually solved by either applying heavy duty motors, large transmission ratios, or parallel elastic elements, such as springs. Heavy duty motors lead to excessive installation of power, which can lead to inefficient and unsafe Actuators. High transmission ratios lead to high losses and insufficient “backdrivability” of the actuator device from the side of the load, which is important in a haptic application. Parallel springs mean installation of additional elements, which can also be heavy and bulky. This is undesired if weight and space are constrained.

A second challenge in haptic devices is to avail of fine force control. This challenge is often solved by using springs in series to a motor, following the principle of series- elastic actuation. By deliberately decoupling load and motor in such a compliant way, motor dynamics can better be hidden and force can be controlled better.

The invention is aimed at meeting the above challenges and providing an actuator device according to the preamble, which can be equipped at the same time with both limited motor capacity and accurate fine force control.

The actuator device of the invention is therefore provided with the features of one or more of the appended claims.

In a first aspect of the invention the first center of rotation and the second center of rotation are distant from each other, and the driving member connects via a connecting element to at least one elastically resilient element, wherein on their end or ends distant from the driving member said elastically resilient element or elements is/are connected to a distant part or parts of the driven member.

In a preferred embodiment the connecting element is provided between and connects to an even number of elastically resilient elements, which are located on opposite sides of the driving member.

In a suitable embodiment the even number of resilient elements counts two.

The invention thus relates to a nonlinear actuation principle that exploits at least one, but preferably two, or in general an even number of (mechanical) elastically resilient elements that are assigned a dual function: to note as series and as parallel elements in combination with a motor. This way, a compact actuator device can be realized, with both high torque capabilities near the end of the range of motion (for the bicycle

- 3 = simulator, that means for a large lean angle), thanks to parallel elastic effects, but also fine force control possibilities thanks to elastic effects in series.

Most commonly it is advantageous that in a neutral position wherein the driving member is in line with the first center and the second center of rotation, the elastically resilient elements have identical properties and are symmetrically arranged between the driving member and the driven member,

To achieve best results it is beneficial that in the neutral position wherein the driving member is in line with the first center and the second center of rotation, the elastically resilient elements are pretensioned.

It is noted that the driving member has a different, preferably smaller length between the first center of rotation and the connecting element of the two elastically resilient elements than the length of the driven member between the second center of rotation to where the elastically resilient elements are connected to the driven member. This feature relates to the effects that are achievable with the actuator device of the invention.

Instead of making the driving member smaller, also other relationships of the dimensions are possible, for example the ratio of aforementioned lengths could alternatively be chosen inverse, such that a bistable property of the driven member results from the spring effect in the case where the motor provides little or no torque.

In the actuator device of the invention it is possible that an indication of a torque exerted on the driven member is derived from a measured length of the elastically resilient elements.

Alternatively or additionally it is also possible that an angular rotation of the driving member and/or the driven member is measured and used as an indication of a torque exerted on the driven member.

In order to optimize the actuator, also for maintaining the installed power of the motor as low as possible, it is preferable that the driving member is actuated by a motor through a belt drive or geartrain. This also makes possible that the motor is distant from the first center of rotation of the driving member.

One preferred mode of applying the invention is that the actuator device is embodied as a bicycle simulator, wherein the driven member forms part of the simulated bicycle.

The accompanying drawing, which is incorporated into and forms a part of the specification, illustrates one or more embodiments of the present invention and, together with the description, serves to explain the principles of the invention.

The drawing is only for the purpose of illustrating one or more embodiments of the invention and is not to be construed as limiting the invention.

In the drawing: -figure 1 shows a schematic principle of the invention; -figure 2 shows an embodiment of the actuator device of the invention in a bicycle simulator; -figure 3 shows the embodiment of figure 2 in a 3D rendering; -figure 4 shows a view at the actuator device of the invention embodied in a bicycle simulator; and -figure 5 shows a complete view of the actuator, wherein most of it is hidden inside fake bags and below a raised floor.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

With reference first to figure 1 the principle of the invention is elucidated, to note: - a driven member 5 is rotatable about an axle 6. — this driven member 5 is actuated by means of a rotary actuator (which can be a motor or a conventional motor- gearing combination) with axle 4.

- the rotary actuator drives a crank (driving member 2) that is connected to the driven member 5 by means of one or more elastic elements 8, 9. — Points 4 and 6 do not coincide, and are in fact separated from each other by a substantial distance h. Preferably h is substantially larger than the length of the driving member 2. — the elastically resilient elements 8, 9 are connected to a connecting element 7 at Q2 and Q1, respectively.

More specifically: The distance between 4 and 6, which can be seen as an eccentricity of the rotary actuator’s center of rotation 4 with respect to the driven member 5 center of rotation 6, leads to the elastically resilient elements 8, 2 taking on dual roles: 1. The elastically resilient elements 8, 3 function in parallel with the driving member 2 in terms of a component that points in direction of the axle 4 (so parallel to a line connecting Q2 and 4), and which does not produce a moment with respect to point 4. The actuator’s geometry is preferably chosen in such a way that this component is zero or close to zero when the mechanism is centered (so symmetric to the line 6-4). 2. The elastically resilient elements 8, 9 function in series with the driving member 2 in terms of the component that is orthogonal to the direction defined by the line connecting Q2 and 4.

The first effect alleviates the rotary actuator of having to produce high moments at the workspace edges. The second effect turns the mechanism into a type of “Series Elastic

Actuator”.

The principle of the invention as explained with reference to figure 1 can be employed in an exemplary embodiment which is depicted in figures 2 and 3, wherein the actuator device 1 is used to actuate the lean degree of freedom in a bicycle simulator (so rotation about an axis that points forward, in driving direction). The elastic elements 8, 9 in this case are two symmetrically arranged linear-elastic tension springs. The springs also have pre-tension when in the neutral configuration.

Note that the chosen electric motor’s axle itself needs not to be located directly at point 4 but can be located further down and connected via a belt drive 10 to the driving member (crank) 2 rotating about point 4. This belt transmission 10 is chosen in order to increase the moment, by a conventional gearing ratio, and also to mount the motor 3 below point 6, such that the large electric motor 3 can be hidden from view in the bike simulator.

In this simulator, for safety purposes the lean angle must be limited in a compliant way. This is achieved by the elastic elements 8, 9. Another advantage of the chosen mechanism for this application is that it is expected that gravity acting on the bicycle simulator and on a human rider will create a moment with respect to point 6 that increases with the sine of the lean angle. That means that in the neutral (upright) position, gravity produces no moment, while at the edges of the workspace, a high moment is expected for a heavy rider. The mechanism can be dimensioned in such a way that the motor 3 needs to produce no or only small torques to compensate for gravity across the entire workspace, thereby allowing for a smaller motor that is only responsible for rendering dynamic effects on the simulator.

Another advantage of the chosen mechanism for this application is that the actuator moment acting on the bicycle (driven member 5) can be measured by measuring the length of the elastic elements 8, 9, or the angles of the crank (driving member 2} and the bike, or combinations of these measurements, in combination with Hooke’s law.

Another advantage of the chosen mechanism for this embodiment 1s that the moment can be controlled precisely by means of a force feedback loop.

Fig. 4 shows how the lean actuator device is connected to a stationary bicycle, to enable simulating lean torques in a simulator.

Fig. 5 also shows an impression of the complete bicycle simulator, showing how the lean actuation mechanism is hidden from view inside of fake bike bags. The motor is mounted below the raised floor. The simulator also has actuators for the steering and for the pedaling motion, but these are not shown.

Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the append-ed claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment.

The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.

Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, mone of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguration of their relationships with one another.

Aspects of the invention are itemized in the following section. 1. Actuator device (1) comprising a driving member (2) that is motor (3) driven and swivable around a first center of rotation (4), and a driven member (5) that is swivable around a second center of rotation (6), characterized in that the first center of rotation (4) and the second center of rotation (6) are distant from each other, and the driving member (2) connects via a connecting element (7) to at least one elastically resilient element (8, 9), wherein on their end or ends distant from the driving member (2) said elastically resilient element or elements (8, 9) is/are connected to a distant part or parts (5, 5'’) of the driven member (5). 2. The actuator device of claim 1, characterized in that the connecting element (7) is provided between and connects to an even number of elastically resilient elements (8, 9), which are located on opposite sides of the driving member (2). 3. The actuator device of claim 2, characterized in that the even number of resilient elements (8, 9) counts two. 4. The actuator device of any one of claims 1 - 3, characterized in that in a neutral position wherein the driving member (2) is in line with the first center of rotation (4) and the second center of rotation (6), the elastically resilient elements (8, 9) have identical properties and are symmetrically arranged between the driving member (2) and the driven member (5). 5. The actuator device of claim 4, characterized in that in the neutral position wherein the driving member (2) is in line with the first center of rotation (4) and the second

- Gg - center of rotation (6), the elastically resilient elements (8, 9) are pretensioned. 6. The actuator device of any one of claims 1 - 5, characterized in that the driving member (2) has a different, preferably smaller length between the first center of rotation (4) and the connecting element (7) of the two elastically resilient elements (8, 9) than the length of the driven member (5) between the second center of rotation (6) to where the elastically resilient elements (8, 9) are connected to the driven member (5). 7. The actuator device of any one of claims 1 - 6, characterized in that an indication of a torque exerted on the driven member (5) is derived from a measured length of the elastically resilient elements (8, 92). 8. The actuator device of any one of claims 1 - +, characterized in that an angular rotation of the driving member (2) and/or the driven member (5) is measured and used as an indication of a torque exerted on the driven member (5). 9. The actuator device of any one of claims 1 - 8, characterized in that the driving member (2) is actuated by a motor (3) through a belt drive (10) or geartrain so as to enable that the motor (3) is distant from the first center of rotation (4) of the driving member (2). 10. The actuator device of any one of claims 1 - 9, characterized in that the actuator device (1) is embodied as a bicycle simulator, wherein the driven member (5) forms part of the simulated bicycle.

Claims (10)

Conclusions 1. Actuator device (1) comprising a drive member (2) driven by a motor (3) and pivotable about a first pivot (4), and a driven member (5) pivotable about a second pivot (6), characterised in that the first pivot (4) and the second pivot (6) are spaced apart, and the drive member (2) is coupled via a connecting element (7) to at least one elastically resilient element (8, 9), said elastically resilient element or elements (8, 9) being connected at their end or ends spaced from the drive member (2) to a spaced portion or portions (5', 5'') of the driven member (5). 2. Actuator device according to claim 1, characterised in that the connecting element (7) is arranged between and coupled to an even number of elastically resilient elements (8, 9) located on either side of the drive member (2). 3. Actuator device according to claim 2, characterised in that the even number of resilient elements (8, 9) is two. 4. Actuator device according to any one of claims 1 to 3, characterised in that in a neutral position in which the drive member (2) is aligned with the first pivot point (4) and the second pivot point (6), the elastically resilient elements (8, 9) have identical properties and are arranged symmetrically between the drive member (2) and the driven member (5). 5. Actuator device according to claim 4, characterised in that in the neutral position in which the drive member (2) in line with the first pivot point (4) and the second pivot point (6), the elastically resilient elements (8, 9) are prestressed. Actuator device according to any one of claims 1 to 5, characterised in that the drive member (2) has a different, preferably smaller length between the first pivot point (4) and the connecting element (7) of the two elastic resilient elements (8, 9) than the length of the driven element (5) between the second pivot point (6) where the elastic resilient elements (8, 9) are connected to the driven element (5). 7. Actuator device according to any one of claims 1 to 6, characterised in that an indication of a torque exerted on the driven member (5) is derived from a measured length of the elastically resilient elements (8, 9). 8. Actuator device according to any one of claims 1 to 9, characterised in that an angular displacement of the drive member (2) and/or the driven member (5) is measured and used as an indication of a torque exerted on the driven member (5). 9. Actuator device according to any one of claims 1 to 8, characterised in that the drive member (2) is driven by a motor (3) via a belt drive (10) or gear transmission to enable the motor (3) to be arranged at a distance from the first pivot point (4) of the drive member (2). 10. Actuator device according to any one of claims 1 to 3, characterised in that the actuator device (1) is designed as a bicycle simulator, whereby the driven member (5) forms part of the simulated bicycle.