ITPI20110057A1 - NON-LINEAR ELASTIC MECHANISM WITH PROGRAMMABLE CHARACTERISTICS - Google Patents

Description

DESCRIPTION

CHARACTERISTIC NON-LINEAR ELASTIC MECHANISM

PROGRAMMABLE

The present invention relates to a non-linear elastic mechanism with programmable characteristic of the type specified in the preamble of the first claim.

In detail, the present invention relates to a non-linear elastic mechanism suitable for connecting one or more first elements to a single second element and for connecting these elements to each other by varying, in a non-linear manner, the characteristic of the connection created, causing a variation in intensity. of the reciprocal response in a way that is not proportional to the input function such as, for example, a displacement.

In particular, the invention concerns a mechanism that can be used in a robot, or in any other device equipped with suitable organs that allow the device itself to perceive the surrounding environment and interact with it. This mechanism can therefore be used in all those situations in which a robot interacts with or is in the vicinity of a user such as, for example, in the industrial field or in service and domestic robotics.

As is known, industrial automation involves the use of robots or the like for control and production which increasingly replace the human operator at least for the material execution of the operations.

These robots usually consist of a fixed base, a series of intermediate elements that can be moved reciprocally by means of motors and an end member, such as a gripper or other work tool, suitable for carrying out a process, such as a gripping and releasing operation.

One of the most important components of the robot is certainly identifiable in a mechanism, usually called an actuator, which is constituted by a joint able to loosely constrain two of the aforementioned components of a robot and by one or more motors which reciprocally move these components.

In recent years, in order to improve the safety and working precision of these robots, various non-linear elastic mechanisms have been devised, that is, actuators capable of varying their compliance guaranteeing, at every moment, excellent processing quality and high safety.

These particular mechanisms, ie the actuators, are constituted by a structure able to contain the various elements making up these mechanisms and bound to a first component; by two input pulleys connected to two motors; by an output pulley connected to a second component of the robot which is adapted to be moved with respect to said first component; by one or more wires, cables or belts or other similar elements able to functionally connect the pulleys so as to transmit the motion from the motors to the second component; and by springs suitably connected to said wires / cables in such a way as to allow the aforementioned transfer of motion regardless of the voltage present on said wires / cables.

Some examples of such non-linear elastic mechanisms are described in US patents 2006/0113846 A1 and EP10188315.5.

The aforementioned known technique has some important drawbacks.

A first drawback of the known non-linear elastic mechanisms is that they are particularly complex in the manufacturing phase of the actuators themselves.

In particular, this complexity is substantially due to the difficult positioning and constraint of the wires / cables.

In fact, in order to avoid slippage of the wires / cables with respect to the pulleys, it is necessary that they be rigidly bound to the aforesaid pulleys by means of complex knots or suitable anchoring devices.

This wire-pulley connection, being very complex, is difficult to automate and, therefore, requires, for its realization, an operation carried out manually by an operator.

Furthermore, these manual operations, since the dimensions of these mechanisms are particularly small, are extremely complex also in consideration of the fact that the operator is forced to operate in a very small environment. Another defect is therefore represented by the high cost of manufacturing the known mechanisms.

A further problem of such non-linear elastic mechanisms is represented by poor adaptability. In fact, in order to modify the yield variation curve, they require the replacement of almost all of the components and, therefore, the execution of complicated operations.

Another problem is the limited range of compliance values obtainable with the known mechanisms since, due to the need to constrain the wires / cables to the pulleys, it limits the stroke of the pulleys to the length of the wire / cable portion wound on it.

In this situation, the technical task underlying the present invention is to devise a non-linear elastic mechanism with a programmable characteristic capable of substantially obviating the aforementioned drawbacks.

Within the scope of said technical task, an important object is to obtain an inexpensive non-linear elastic mechanism which is simple to manufacture.

An important object of the invention is therefore to devise a simple and inexpensive non-linear elastic mechanism.

A further object of the invention is to provide a non-linear elastic mechanism capable of varying the compliance variation function in a particularly simple way.

The technical task and the specified aims are achieved by a non-linear elastic mechanism with programmable characteristic as claimed in the attached Claim 1.

Preferred embodiments are highlighted in the sub-claims.

The features and advantages of the invention are clarified below by the detailed description of a preferred embodiment of the invention, with reference to the accompanying drawings, in which:

Fig. 1 shows a perspective view of a non-linear elastic mechanism according to the invention;

Fig. 2 shows a front view of the non-linear mechanism of Fig. 1; Fig. 3 shows a section of the non-linear non-linear elastic mechanism of Fig. 2;

Fig. 4 presents a sectional view of a particular non-linear elastic mechanism according to the invention;

Fig. 5 is an exploded view of the mechanism of Fig. 4;

Fig. 6 represents a possible application of the non-linear elastic mechanism of Fig 4.

With reference to the cited Figures, the non-linear elastic mechanism with programmable characteristic according to the invention is globally indicated with the number 1.

It is able to connect one or more first elements to a single second element in a non-linear way. In particular, the mechanism 1 in the event of a stimulus, such as for example an impact or an obstacle during a motion, is able to determine a response to this stimulus which varies in a non-linear manner according to the characteristic of the mechanism itself. For example, as better specified below, it allows a relative motion between these elements which varies as a function of the characteristic of the non-linear elastic mechanism 1.

The mechanism 1 therefore comprises at least one transmission apparatus 1a adapted to functionally connect one of said first elements to the second element, that is, adapted to connect said two elements allowing them to reciprocally transmit forces and / or motion.

In detail, the transmission apparatus 1a includes at least a first toothed wheel 2 capable of being connected to the first element and defining a first axis of rotation 2a; at least a second toothed wheel 3 which is engaged with the first wheel 2 and adapted to be connected to the second element and which defines a second axis of rotation 3a; elastic means 4 functionally interposed between the second toothed wheel 3 and the relative second element; and, in some cases, bearings 5 or other similar components designed to reduce friction during the motion of wheels 2 and 3.

Finally, to facilitate the functional connection between the second wheel 3 and the second element and, more precisely, between the elastic means 4 and the second element, the non-linear elastic mechanism 1 can have a base structure 6 suitable for supporting the transmission 1 a and to functionally interpose between the elastic means 4 and the second element.

The expression "toothed wheels" identifies all those mechanical components with teeth designed to allow said mechanical components to engage each other so as to allow the passage of motion between these components. Therefore the wheels 2 and 3 can be simple toothed wheels, ie with straight teeth, helical toothed wheels, racks or other similar mechanical component. Preferably at least one of the wheels 2 and 3 is a toothed wheel with a non-circular profile and, more preferably still, both the first toothed wheels 2 and the second wheels 3 are non-circular toothed wheels. In particular, the expression "non-circular toothed wheels" identifies all those toothed wheels having a non-circular profile and, therefore, characterized by a variable radius.

These toothed wheels can therefore have any profile and, for example, a curvilinear profile (elliptical, spiral, etc.). Preferably, the wheels 2 and 3 have a curvilinear profile and, more preferably, these wheels have a spiral profile, as shown in Fig. 1.

In particular, the profile of the toothed wheels 2 and 3 is further characterized by the presence of, respectively, a first engagement portion 2b and a second engagement portion 3b adapted to mutually overlap so as to define a locking position of the wheels 2 and 3.

Functionally interposed between the second wheel 3 and the corresponding element, the transmission apparatus 1a has, as described above, the elastic means 4, that is, means suitable for varying its own force exerted on the basis of an elongation or torsion of the means themselves. . In particular, these elastic means 4 are of the linear type and, therefore, adapted to vary the force exerted in a manner directly proportional to their elongation / torsion and, therefore, can comprise compression springs, traction springs or, as shown in Figs. 1-3, torsional springs.

Said elastic means 4 functionally connect the second toothed wheel 3 to the relative second element and, preferably, functionally connect the second wheel 3 to the structure 6. In particular, the aforementioned functional connection is made in such a way that the means 4, as better described below described, mutually connect the aforementioned components, ie the wheel 3 and the structure 6, in such a way that each of them, through the elastic means 4, discharges any force on the other component or transmits a motion to it.

Therefore, in order to allow this connection, the elastic means 4 can have, as shown in Fig. 3, one end constrained to the second toothed wheel 3 in correspondence with a notch made near the second axis 3a and the other end constrained to the base structure 6 in correspondence with a special coupling obtained in structure 6.

The applicant, thanks to careful observations, has noticed that, through a particular arrangement of the connection apparatuses 1a, the non-linear elastic mechanism 1 allows to perform, as described below, a connection with variable compliance between two or more first elements and a unique Second element. In particular, he observed that the mechanism 1 can be used, in an advantageous and innovative way, for the realization of a robot 100 allowing to realize a kinematic connection with variable compliance between, for example, two arms 101 of the robot 100. More precisely, this particular mechanism 1 allows to obtain a connection adapted to move a first arm 101 with respect to a second arm 101 or to a support base to which the robot 100 is constrained and which allows the compliance of said connection to be varied.

The expression robot identifies any device suitable for use in the industrial field for handling and assembly operations and, for example, for handling and assembling small parts, such as circuits and components. Furthermore, this term robot also refers to service robotics devices and prostheses, ie mechanical devices designed to replace a missing part of the body, such as a limb, or to integrate a damaged part.

In this case, as shown in Fig. 6, the second element can be identified in a first arm 101 of the robot 100, while the first element can be identified in a motor 7 suitably housed inside the support base or in the aforementioned second different arm 101.

The motors 7 are preferably of the electric type and powered by a power supply system, not shown in the figure, which can be constituted by internal batteries or by suitable cables or contacts suitable for putting the motors 7 in connection for the passage of current with an external source. In particular, each motor 7 is a servomotor, i.e. a device consisting of an electric motor equipped with mechanical reduction, a feedback system equipped with at least one sensor and suitable for controlling the position of the axis of the motor itself, and control electronics. adapted to regulate the operation of the motor 7 and, therefore, of the non-linear elastic mechanism with programmable characteristic 1.

In this particular case, as shown in Fig. 4, the non-linear elastic mechanism 1 has at least two transmission apparatuses 1a, each of which is able to functionally connect a first element, i.e. a motor 7, to the only second element, i.e. one arm 101.

In particular, as illustrated in Figs. 4 and 5, this elastic mechanism 1 provides for a single base structure 6 which is capable of being functionally connected, by means of the elastic means 4 of the two transmission apparatuses 1a, to both second wheels 3 of said two apparatuses 1a, is to be rigidly constrained to an arm 101 by means of screws, joints or other solution capable of making arm 101 and the single base structure 6 integral with each other.

In this case, the two transmission apparatuses 1a are arranged on the opposite side with respect to the base structure 6 and each of them advantageously has two first toothed wheels 2 connected to one of the two motors 7 and two second toothed wheels 3 each of which has elastic means 4 adapted to functionally connect the second wheel 3 to the base structure 6.

In detail, the two first wheels 2 of each apparatus 1a are almost superimposed and have the first rotation axes 2a substantially coinciding with each other, while the two second wheels 3 are preferably substantially symmetrically placed with respect to the first rotation axis 2a. More preferably still, the first axes of rotation 2a of the first toothed wheels 2 of the two transmission apparatuses 1a are substantially coincident with each other.

In order to ensure correct motion between the various components of the robot 100, the mechanism 1 can have a connection member 8 comprising reciprocal movement means, such as for example bearings and bushings, suitable for interposing between an arm 101 and the base structure 6 allowing a relative motion between the two arms and, in particular, the motors 7 and the arm 101 constrained to the base structure 6.

The operation of a non-linear elastic mechanism with programmable characteristic, described above in a structural sense, is as follows.

For reasons of clarity, a first example of non-binding operation is initially described in which reference is made to a possible use of an elastic mechanism 1 equipped with a single transmission apparatus 1a.

In particular, the operation refers to the use of the mechanism 1 for the static compensation of a mechanical arm substantially adapted to maintain a position independently of external agents, i.e. of a mechanical arm which is constrained to the base by means of the mechanism 1 and which, in following external actions such as gravity or an impact, is able to define any position of equilibrium and, therefore, of non-movement with respect to the base.

In this case, the non-linear elastic mechanism 1 has the base structure 6 integrally constrained to said support base, while the first wheel 2 is constrained to the arm which, in this case, identifies the first element.

Initially, the system presents itself in an initial equilibrium condition, ie with the arm in a vertical position and the non-linear elastic mechanism 1 in the unloading configuration. In detail, in this unloaded condition the transmission apparatus 1a has the elastic means 4 in a rested condition and, therefore, unloaded, while the toothed wheels 2 and 3 coupled in such a way that the first wheel 2 has the spoke part lower coupled with the portion of the second toothed wheel 3 with larger radius, as illustrated in Fig. 1.

When the arm begins to tilt, for example, due to an impact, the non-linear elastic mechanism 1 is unable to oppose the motion and, therefore, the arm begins to move causing the rotation of the two toothed wheels 2 and 3 and, consequently, the loading of the elastic means 4.

In detail, this rotation increases the radius of the portion of the first toothed wheel 2 engaged with the second wheel 3 and decreases the corresponding portion of said second toothed wheel 3. At the same time, this rotation begins to elastically deform the elastic means 4 which, as a result, they begin to accumulate energy and, therefore, to charge.

Therefore, this displacement of the arm causes the non-linear elastic mechanism 1 to start exerting on the arm itself a force in the opposite direction to that of the motion and which counteracts the moment generated by the force of gravity and due to the no longer vertical position of the arm. In detail, this force is determined by the combination of the linear force exerted by the elastic means 4 with the variation of the ratio between the radii of the portions of the toothed wheels 2 and 3 mutually engaged.

In conclusion, the mechanism 1 exerts on the arm a force that grows in a non-linear way as the arm moves away from the aforementioned initial position and which therefore, through an appropriate dimensioning of the toothed wheels 2 and 3 and of the means 4, allows to maintain the arm in any inclined position using a mechanism 1 equipped with a single transmission apparatus 1 a.

On the contrary, if the mechanism 1 is used to connect together, for example, two arms 101 of a robot 100, moving them reciprocally and, at the same time, varying the stiffness of the connection between these components, the operation of a mechanism non-linear elastic with programmable characteristic 1 is the following.

Initially, the mechanism 1 is in a condition of maximum compliance, ie with the two transmission apparatuses 1a in the unloaded condition. In detail, each transmission apparatus 1a has the first toothed wheels 2 and the second wheels 3 engaged respectively in correspondence with the portion with minimum radius and maximum radius.

In this configuration, when the arm 101 integral with the base structure 6 undergoes, for example, an impact, there is only a displacement of this arm 101 while the motors 7 and the other arm 101 remain substantially stationary.

In fact, this impact is substantially absorbed by the non-linear elastic mechanism 1 and, therefore, there is only a displacement of only the arm 101 constrained to the base structure 6 which, being directly proportional to the compliance, is relatively high.

This displacement is, in fact, absorbed by a variation in the position of the components constituting each of the two transmission apparatuses with respect to the motor elative. More precisely, the absorption is carried out through a combination of the reciprocal movement between the toothed wheels 2 and 3 and a deformation of the four elastic means 4 which, being substantially unloaded, require a high deformation to absorb the impact.

If it is intended to move the arm 101 constrained in correspondence with the base structure 6, the motors 7 are activated which rotate the respective first toothed wheels 2 and, therefore, the two transmission apparatuses 1a, imposing the same speed and the same direction of rotation.

In particular, this activation of the two motors 7, thanks also to the presence of the connection member 8, allows to move the arm 101 constrained to the structure 6 with respect to the rest of the robot 101 and, in particular, to the two motors 7. Alternatively, if it is decided to reduce the compliance of the mechanism 1, the motors 7 are activated by making the first toothed wheels 2 of the transmission 1a rotate with speeds different from each other in module and / or in the direction. In particular, this action causes the first toothed wheels 2 to rotate with respect to the corresponding second toothed wheels 3, causing an elastic deformation of the elastic means 4 and, therefore, a loading of the means themselves.

In detail, the reduction of the compliance of the elastic mechanism 1 is of the non-linear type as it occurs on the basis of the variation of the above described response of the transmission apparatuses 1a.

In fact, the variation in compliance depends on the shape of the toothed wheels 2 and 3 and on the type of elastic means 4 used and, in the particular case in which the wheels 2 and 3 have a suitable spiral profile and the means 4 are constituted by torsional springs , this variation is exponential.

Once the compliance of the mechanism 1 has dropped to the desired value, if one of the two arms 101 undergoes a shock substantially of the same intensity as the previous one, the relative displacement of the arm 101 is of lesser extent since the non-linear elastic mechanism 1, thanks to the new compliance condition, opposes with greater resistance thanks both to the fact that the elastic means 4 are at least partially loaded and to the fact that the toothed wheels 2 and 3 have a different mutual arrangement.

Finally, if it is decided to reduce the compliance and, for example, return it to the initial configuration, it is sufficient to operate the motors 7 in the opposite way so as to move the toothed wheels 2 and 3 in such a way as to at least partially unload the elastic means 4.

The invention allows important advantages.

A first advantage of the non-linear elastic mechanism 1 is represented by the fact that it allows to obtain, in a simple and fast way, a shock absorber.

In fact, thanks to the particular combination of non-circular toothed wheels and the elastic means 4, the mechanism 1 is able to vary its own elastic coefficient extremely so as to absorb an impact with small displacements.

Another advantage, typical of the mechanism 1, is given by the extreme simplicity of construction and, therefore, by the reduced cost.

A further advantage is given by the possibility of varying the compliance variation function simply by mounting different toothed wheels 2 and 3. In particular, it is possible to select the compliance variation function in a practical and quick way, adapting it to the particular requirements.

This aspect also allows to have a non-linear elastic mechanism with programmable characteristic 1 with a range of values of compliance that can be assumed much wider than those possible with known actuators.

A not secondary advantage is represented by the presence of the engagement portions 2b and 3b which allows to define a locking position and, therefore, to ensure that the two wheels 2 and 3 mesh completely to cover the entire profile of the wheels themselves without that the mechanism 1 and, more precisely, the toothed wheels 2 and 3 lose their meshing.

Another advantage is given by the particular arrangement of the wheels (toothed 2 and 3 of each transmission apparatus 1a. In particular, the symmetrical arrangement of the toothed wheels 2 and 3 allows to have a substantial balance between the forces involved and, therefore, a high operating stability.

The invention is susceptible of variants falling within the scope of the inventive concept. All the details can be replaced by equivalent elements and the materials, footprints and dimensions can be any.

Claims (10)

CLAIMS CHARACTERISTIC NON-LINEAR ELASTIC MECHANISM PROGRAMMABLE 1. Non-linear elastic mechanism (1) with programmable characteristic adapted to connect at least a first element to a second element comprising at least one transmission apparatus (1a) adapted to functionally connect one of said at least one first element to a second element and comprising at least a first toothed wheel (2) able to be connected to said first element and defining a first axis of rotation (2a) and at least a second toothed wheel (3) able to be connected to said second element and defining a second axis of rotation ( 3a); said toothed wheels (2, 3) being mutually engaged; and characterized in that at least one of said toothed wheels (2, 3) is a toothed wheel with a non-circular profile; and in that said transmission apparatus (1a) comprises elastic means (4) functionally interposed between said at least one second toothed wheel (3) and said second element. 2. Non-linear elastic mechanism (1) according to claim 1, wherein at least one of said toothed wheels (2, 3) is a toothed wheel with a spiral profile. Non-linear elastic mechanism (1) according to one or more of the preceding claims, wherein both said at least one first toothed wheel (2) and said at least one second toothed wheel (3) are non-circular toothed wheels. 4. Non-linear elastic mechanism (1) according to the preceding claim, both said at least one first toothed wheel (2) and said at least a second toothed wheel (3) respectively comprise a first engagement portion (2b) and a second engagement portion ( 3b) adapted to overlap, defining a locking position of said wheels (2, 3). 5. Non-linear elastic mechanism (1) according to one or more of the preceding claims, comprising a base structure (6) able to support said at least one transmission apparatus (1a) and to functionally interpose between said elastic means (4) and said second element (3). 6. Non-linear elastic mechanism (1) according to one or more of the preceding claims, comprising at least two of said at least one transmission apparatus (1a); wherein said at least two transmission apparatuses (1a) are adapted to functionally connect at least two of said at least one first element, said second element; and in which said at least two transmission apparatuses (1a) are adapted to be moved independently from each other so as to vary the compliance between said second element and said at least two first elements. 7. Non-linear elastic mechanism (1) according to the preceding claim, in which said at least two transmission apparatuses (1a) are arranged on the opposite side with respect to said base structure (6). 8. Non-linear elastic mechanism (1) according to the preceding claims 6-7, in which each of said at least two transmission apparatuses (1a) comprises two of said at least one first toothed wheel (2), and in which said first axes of rotation (2a) of said two first toothed wheels (2) of said at least two transmission apparatuses (1a) are substantially coincident. 9. Non-linear elastic mechanism (1) according to one or more of claims 6-8, comprising two of said at least one second toothed wheel (3); and in which said elastic means (4) are adapted to functionally connect each of said two second toothed wheels (3) with said base structure (6); 10. Non-linear elastic mechanism (1) according to the preceding claim, in which said second rotation axes (3a) of said two second toothed wheels (3) are substantially symmetrically placed with respect to said first rotation axis (2a). 1. Nonlinear elastic mechanism (1) having programmable characteristic suitable to connect at least one first element to a second element and comprising at least one transmission apparatus (1a) suitable to connect one of said at least one first element to said second element and comprising at least one first gear wheel (2) suitable to be connected to said first element and defining a first axis of rotation (2a) and at least one second gear (3) suitable to be connected to said at least one second element and defining a second axis of rotation (third), said gears (2, 3) being engaged to each other, and characterized by the fact that at least one of said gears (2, 3) is a non-circular gear, and by the fact that said at least one transmission apparatus (1a) comprises elastic means (4) functionally interposed between said at least one second gear (3) and said second element. 2. Nonlinear mechanism (1) according to claim 1, wherein at least one of said gears (2, 3) is a non-circular gear with spiral profile. 3. Nonlinear mechanism (1) according to one or more of the previous claims, wherein both said at least one first wheel gear (2) and said at least one second gear (3) are non-circular gears. 4. Nonlinear mechanism (1) according to previous claim, wherein said at least one first wheel gear (2) and said at least one second gear (3) respectively include a first engagement portion (2b) and a second engagement portion (3b) suitable to overlap establishing a blocking position of these wheels (2, 3). 5. Nonlinear mechanism (1) according to one or more of the previous claims, comprising a base structure (6) suitable to support said at least one transmission apparatus (1a) and functionally interposed between said elastic means (4) and said second element . 6. Nonlinear mechanism (1) according to one or more of previous claims, comprising at least two of said at least one transmission apparatus (1a), wherein said at least two transmission apparatuses (1a) are suitable to connect functionally at least two of said at least one first element to said second element, and wherein said at least two transmission apparatuses (1a) are suitable to be moved indepen dently of each other so as to modify the stiffness between said element and said at least two first elements. 7. Nonlinear mechanism (1) according to previous claim, wherein said at least two transmission apparatuses (1a) are arranged by opposite sides of said basic structure (6). 8. Nonlinear mechanism (1) in accordance with the previous claims 6-7, wherein each of said at least two transmission apparatuses (1a) includes two of said at least one first gear wheel (2), and wherein said first axes of rotation (2a) of said two first gears (2) are essentially coincident. 9. Nonlinear mechanism (1) according to one or more of previous claims 6-8, wherein each if said at least two transmission apparatuses (1a) includes two of said at least one second gear (3), wherein said elastic means (4 ) are functionally suitable to connect each of said two second gears (3) to said second element 10. Nonlinear mechanism (1) according to previous claim, wherein said second axes of rotation (3a) of said two second gears (3) are placed substantially symmetrically with respect to the first axis of rotation (2a).