WO2015063524A1

WO2015063524A1 - Twisted cord actuating system for robotic arm

Info

Publication number: WO2015063524A1
Application number: PCT/GB2014/053282
Authority: WO
Inventors: Thiago AZEVEDO; Gavin CASSIDY
Original assignee: The Shadow Robot Company Limited
Priority date: 2013-11-04
Filing date: 2014-11-04
Publication date: 2015-05-07
Also published as: GB2519992A; GB201319454D0

Abstract

A linear actuation mechanism for robots and related devices, comprising a one degree of freedom rotating joint moveably between a first and a second position; at least one cord attached to said one degree of freedom rotating joint; means for rotating the at least one cord; and a spring assembly arranged so as to counterbalance the load acting on said one degree of freedom rotating joint, wherein actuation of the means for rotating twists or winds the cord causing the one degree of freedom rotating joint to move from the first to a second position.

Description

TWISTED CORD ACTUATING SYSTEM FOR ROBOTIC ARM

Technical Field

The present invention relates to actuators for use in, for example, robotic applications. In particular, the invention relates to twisted cord actuators. Background

Robots are more frequently being used to perform increasingly complex tasks; hence it is desirable for them to have versatile joints and tendons allowing individual robotic elements to flexibly adapt to environmental tasks and realize complex motions.

Conventional actuators are structurally complex, weighty and outsized and therefore place a strain on the other elements of the robotic system and in particular requiring the remaining actuators to accommodate for the additional weight with additional power. As robotic systems increase in size, complexity and functionality, the number of system components also increase resulting in the need for economically-priced and durable system parts.

Furthermore, high power, force and/or torque generation is required to provide the capabilities in a wide range of robotic load manipulation tasks. However, at the same time, the force or torque generation must be precisely controlled to enable interaction with the robot's environment without causing damage to either the environment or the robot itself. Indeed, shock tolerance is required of robotic actuator systems because the chance of unexpected or unpredictable high-force interactions with task and load manipulation environments is greatly increased in such complex applications.

These actuator attributes are in contradiction. For example, to achieve a decrease in actuator weight, gears are conventionally introduced in an actuator employing a motor. Although a gear train does lighten the system by allowing for use of a smaller motor operating at higher speeds, it also sensitizes the system to shock loads. Shock-induced damage of gear trains is known to be one of the most common causes of actuator failure. In an effort to enhance gear train strength to reduce gear damage, precise materials and designs are often employed for gear systems. Typically such systems are prohibitively expensive and therefore are not acceptable for common robotic actuation applications.

As such, there exists a need for an actuator which aims to provide a strong, inexpensive, light weight, durable, shock resistant and accurate force control output which overcomes at least some of the disadvantages of the existing actuators. Preferably, such actuating mechanisms will closely perform and maintain the same physical function and configuration as a human arm.

Therefore, it is an object of the invention to provide an improved robotic arm. Summary

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The invention provides an actuator that attempts to overcome limitations of conventional actuators to achieve precise force control and force control stability with a strong, inexpensive, high power and force or torque generation, light weight and shock resistant actuator design. Actuation of a robotic element is optimally provided by an actuator that is light weight and low cost.

This invention provides a robotic arm comprising a linear actuation mechanism for robots and related devices, comprising a one degree of freedom rotating joint moveable between a first and a second position. In addition there is at least one cord attached to the said one degree of freedom rotating joint; and furthermore there is means for rotating the at least one cord; and a biasing assembly arranged so as to counterbalance the load acting on said one degree of freedom rotating joint, and wherein actuation of the means for rotating twists or winds the cord causing the one degree of freedom rotating joint to move from the first to a second position. The biasing assembly may be a spring assembly or alike or alike.

Preferably, the linear actuation mechanism consists of at least one cord which comprises of two cords attached to the one degree of freedom rotating joint. The cords are arranged as a agonist/antagonist pair, such that actuating the first cord rotates said one degree of freedom rotating joint from the first to the second position and actuating the second cord rotates said one degree of freedom rotating joint from the second to the first position. Preferably, the linear actuation mechanism comprises the means for rotating at least one cord comprising a motor assembly and wherein the motor assembly comprises one motor for each cord. Furthermore, the linear actuation mechanism may comprise four cords and four means for rotating said cords.

Twisted cord actuation provides a number of benefits such as lower costs, through a reduction in the need for gearing a motor output, and lower mass, as the twisted cords act as lightweight gearing capable of outputting linear motion from rotatory motion. Preferably, the linear actuation mechanism contains a biasing assembly comprising one or more springs attached to the one degree of freedom rotating joint. Preferably, the linear actuation mechanism comprised at least one cord attached to one or more hinged level members provided on the one degree of freedom rotating joint. Advantages of the biasing assembly are that they help reduce the amount of load the cords have to bear. A major problem is that cords suffer wear and tear and therefore require replacement at numerous times during the life of the actuator. By reducing the effective load on the cords through the use of spring assemblies, the usable life of the cords may be significantly extended, thereby reducing the amount of down time of the arm when the cords are being replaced and/or maintained.

Furthermore, biasing assemblies are feasible as its addition to the design is inexpensive, whilst the cords are attractive for a low cost design due to being a very cost effective means of producing linear, high force movement using low-cost, low-torque DC motors with or without a gearbox.

Preferably, the motor assembly for use with the linear actuating mechanism comprises a motor housing; and a motor moveable between a first and a second position in respect of the housing wherein the motor moves from the first to the second position in use. Additionally, the motor is moveably attached to the housing via a casing. Furthermore, the motor assembly casing comprises pins arranged to cooperate with in apertures in the housing. Preferably, the motor assembly casing further comprises springs arranged around the pins. Preferably the motor moves between the first positions to the second position as a result of the motor being pulled by the linear actuating mechanism in use. The motor source may be geared with a gearbox; such a gear box may be integral to the motor source and in any case is not required for all applications.

Preferably, there is provided a kit assembly for use with the linear actuating mechanism wherein the kit comprises one or more biasing assemblies. The biasing assemblies may be the biasing assemblies. Preferably the biasing assemblies are adapted such that the biasing means are easily replaceable and or interchangeable and or detachable and or adjustable into the robotic arm. Furthermore, there is provided a kit assembly for use with the linear actuating mechanism wherein the kit comprises one or more cord assemblies. The cord of the cord assemblies may be adapted to be user interchangeable and or detachable and or easily adjustable and or replaceable into the robotic arm.

A robotic arm comprising the aforementioned linear actuating mechanism and or optionally comprising the motor assembly. Preferably, a linear actuating mechanism and or optionally a motor assembly and or optionally a robotic arm substantially as hereinbefore described with reference to the accompanying drawings. The preferred features may be combined as appropriate, as would be apparent to a skilled person, and may be combined with any of the aspects of the invention.

Brief Description of the Drawings

The invention is diagrammatically illustrated, by way of example, with reference to the following drawings, in which:

Figure 1A illustrates schematically the components of the robotic arm in a 'bent (or contracted) arm' position; Figure 1 B illustrates schematically the components of the robotic arm in a 'straight (or extended) arm' position;

Figure 1 C illustrates schematically the components of the robotic arm from Figures 1A and 1 B from a different perspective where the robotic arm is forward facing in a substantially extended position; Figure 2 illustrates schematically the base portion of the robotic arm;

Figure 3A illustrates schematically the actuation portion of the robotic arm at a first position in use;

Figure 3B illustrates schematically the actuation portion of the robotic arm at a second position in use; Figure 4 illustrates a side perspective of the components of the robotic arm from Figures 1A to 1C;

Figure 5 illustrates a top perspective of the components of the robotic arm from Figure 4; Figure 6A illustrates a schematically the motor portion of the robotic arm; Figure 6B illustrates a schematically the motor portion of the robotic arm from Figure 6A. Common reference numerals are used throughout the figures to indicate similar features. Detailed Description

Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying figures or may be learned by practice of the invention.

Figures 1A to 1C illustrate schematically the components of the robotic arm. Figure 1A illustrates the motor portion 12 comprising of four motors 102, 104, 106 and 108, preferably arranged in pairs and attached to twisted cords 132, 134, 136 and 138 forming part of the driving mechanism. The preferred twisted cord actuator described herein includes a motor with an axial shaft to which, by a coupling, the single free end of two or more cords are attached. The opposing ends of the cords are attached to the moveable member. As the shaft rotates the cords are twisted around each other in helical fashion. Thus their combined length is shortened.

The rotating device can be taken to represent the muscle and the twisting of the cords, the tendons. The twisting pair of cords may then be threaded through a sheath to act as a pull cable. In most applications the present invention may be matched to the load by the careful selection of the motor, cord diameter, and cord length with the additional use of a biasing assembly (hereinafter referred to as spring assembly, simply). This combination creates a low inertia resilient actuator. The twisted cords 132, 134, 136 and 138 may be strings, ropes, wires or similar (hereinafter referred to as cords, simply) and are preferably twisted loosely. Figure 1 A illustrates an end (a first end) of the twisted cord 132 attached to the output shaft 102B of the motor 102 and the other end (a second end) thereof connected to the object to be driven; in this case the hinge lever member 132 about a shoulder joint 180. During use, the twisted state of the cords is tightened or loosened (i.e. the cord is more or less wound up) in accordance with the rotation direction of the rotation shaft 102B of the motor 102, so that the length of the twisted cord 132 is decreased or increased. As a result, the drive target, the shoulder joint 180 in this example, is driven within a predetermined range. Similar drive mechanism with respect to motors 104, 106 and 108 may be provided as will be discussed in more detail later. Figure 1 B illustrates schematically the components of the robotic arm in 'straight arm', or extended position. The actuation portion 200 of the robotic arm 10 and the upper arm portion 182 are connected by a shoulder joint 180. The shoulder joint 180 enables the upper arm portion 182 to move about axis with respect to the actuation portion 200; the shoulder joint 180 being a one-degree-rotation freedom joint. The upper arm portion 182 and the forearm portion 186 are connected by elbow joint 184. The elbow joint 184 enables the forearm portion 186 to move about axis X₂ with respect to the upper arm portion 182; the elbow joint 184 being a one-degree-rotation freedom joint. It will be appreciated that the upper arm portion 182 and forearm portion 186 may be arranged such that each of the upper arm portion 182 and forearm portion 186 are actuated by a pair of spring assisted twisted cord actuators preferably arranged in agonist / antagonist fashion.

The upper arm portion 182 and forearm portion 186 have a particular preferably predetermined mass, and in addition may be carrying a load, or at least are operable to do so, thereby increasing the overall mass carried by the shoulder joint 180. The inclusion of a spring assembly 150 and 152 is provided to reduce the load on the shoulder joint 180. Preferably, the particular spring assembly 150 and 152 are selected to counterbalance the average expected load on the shoulder joint 180 in use. In this example, the actuator portion 200 of the robotic arm 10 comprises of two rows of springs 150 and 152. The first spring assembly 150 is preferably selected to calibrate the average expected load about cords 132 and 134. A second spring assembly 152 may further be selected to calibrate the average expected load about cords 136 and 138. The spring assemblies 150 and 152, preferably in concert, act with greater force than that exerted by the load of the robot arm 10 being moved in order to effect movement.

The spring assemblies reduce the amount of load the cords 132, 134, 146 and 138 have to bear. A major problem is that cords suffer wear and tear and therefore require replacement at numerous times during the life of the actuator. By reducing the effective load on the cords 132, 134, 146 and 138 by using spring assemblies 150 and 152, the usable life of the cords 132, 134, 146 and 138 is significantly extended, thereby reducing the amount of down time of the robotic arm 10 when the cords 132, 134, 146 and 138 are being replaced and/or maintained. Using spring assemblies 150 and 152 is feasible as their addition to the design is inexpensive, whilst the cords 132, 134, 146 and 138 are attractive for a low cost design due to being a very cost effective means of producing linear, high force movement using low-cost, low-torque DC motors without a gearbox or other addition to the drive train. It will be appreciated that any number of spring assemblies may be provided; but that it is preferably to have one assembly per cord combination (i.e. two cords arranged in agonist/antagonist fashion or one cord operable to facilitate bidirectional movement of the joint). Indeed, it will be appreciated that any alternative arrangement and number of cords may be used as one cord can be looped around the joint to be actuated, or a number of cords can be attached at one or multiple points along the joint to be actuated. Therefore, although the example described herein refers to four cords driven by four motors and two counters balanced by two spring assemblies 150 and 152, any combination of these components can be used, but may require some modification to the system described herein. For example, wherein two cords are not actuated by two separate motors but by one motor, a more complex motor will be required for actuation of both cords.

Figure 1C illustrates schematically the components of the robotic arm 10 from a different perspective where the robotic arm 10 is forward facing and substantially extended. Motors 102, 104 and 108 as illustrated, include an overall frame structure wherein the motor is attached, preferably releasably attached, therein. The lever portion 204 comprises hinged lever members 162, 164, 166, 168 arranged along the shoulder joint 180. Hinged lever member 166 is not illustrated but is positioned at the rear of lever 168. Cord 132 connects the rotation shaft 102B of motor 102 to the hinged lever member 162. Rotation of the shaft 102B causes cord 132 to wind thereby pulling lever 162 towards the direction of the motor 102; which in the exemplified arrangement results in extension of the arm.

It will be appreciated that each of the cord/motor arrangements provides similar functionality, albeit some in opposed directions thereby causing the shoulder joint 180 to move such that the robot arm 10 contracts or bends. It will be also appreciated that the cords maybe user detachable, adjustable and or replaceable. Although not depicted in the figures, the end effector 188 may be attached to commercially available robotic hands or the like.

Figure 2 illustrates schematically the actuation portion 200 of the robotic arm 10. The motor portion 12 comprises four motors 102, 104, 106 and 108, of which only motors 102 and 106 are illustrated. As previously mentioned, although the robot arm 10 is described to comprise of four motors it will be appreciated that any number of motors may be used for actuation and therefore alternative motor arrangements may be used. However, it is preferable for the motors to be arranged in pairs to allow for the use of simple and therefore cheap motors.

Motors 102 and 106 include a housing 102A and 106A respectively which preferably provide motors 102 and 106 with releasable attachment to the base portion 130 of the robotic arm 10. The spring assembly 150 is secured to the shoulder joint portion 180, thereby allowing for connection with the one degree of freedom axel 179, and an opposite end allowing for connection with the fixed axel 205. Preferably and as illustrated, the spring assembly 150 is aligned linearly enclosed between frame structures 171 and 172 of the robotic arm 10. The spring assembly 152 is secured to the shoulder portion 180 in a similar manner in respect of frame structures 173 and 174 of the robotic arm 10.

The spring assemblies 150 and 152 may be balanced in a way that is optimal for the load characteristics to which the device will be subjected. The spring assembly may be carefully balanced such that at the average rated load the robotic arm 10 may carry at the end-effector 188, the load subjected on the twisting cords to approximately zero, or substantially neutral, for both the agonist and antagonist actuators.

Furthermore, the spring assemblies 150 and 152 are extension springs carefully matched so that they exert a force in parallel to the pull action of cords optimized with the expected loads that could be exerted by the robotic arm 10 and thus minimizing, over the life the cords, the load on the cords. The spring assemblies 150 and 152 arrangement reduces the load on the twisted cord actuators 132, 134, 136 and 138, which by its nature is susceptible to wear and tear when actuated under load as twisting cords under load produces considerable friction, which significantly reduces their useful life. Considering the particular geometry and properties of the spring assembly, such a spring assembly may be constructed of e.g. steel, aluminum, delrin, or nylon 66, and/or other suitable material.

The spring assembly (ies) may be an integral structure as illustrated and preferably are lightweight and compact, and exhibit a desired stiffness for a given application. It is preferable that the spring assemblies 150 and 152 actually carry both the load of the robotic arm 10 when the robotic arm 10 is not in use but also when in use, including the load being actuated; as a result, the spring assembly 150 and 152 optimally are of high load carrying capacity suitable for a given load application. It will be appreciated that the springs assemblies 150 and 152 maybe user detachable, adjustable and or replaceable. Furthermore, it is preferable that the spring assembly does not lose energy per compression cycle and that the spring is of geometry that is easy to attach to the actuator driving load element. Although the robot arm 10 is described to comprise of two spring assemblies 150 and 152, it will be appreciated that alternative spring assembly arrangements may be used. It will also be appreciated that the spring assemblies 150 and 152 may be of a nonmetallic type allowing for resilience, duty cycle and efficiency as required by the application of the robotic arm 10. Figure 3A illustrates schematically the actuation portion 200 of the robotic arm 10 at a first position in use. The actuation portion 200 comprising a driving source for force generation by a motor portion 12. The motor portion 12 comprises a motor 102, 104, 106 and 108.

The motor 102 consisting of a rotating output shaft 102B, comprising of a coupling 112. The cord 132 is looped around the coupling 1 12 on one end and then connected to the hinged lever member 162 about the shoulder joint 180 via a secured connection means 302.

The twisted cord 132 in the state as shown has a length L. Rotation about the shaft 102B of the motor 102 results in the twisting or winding of the cord 132. As twisting continues the cord 132 shortens in length by becoming a wound bundle, resulting in length of the cord L being shortened by ΔΙ_. The length of twisted cord 132 thus becomes L - ΔΙ_. As a result, the shoulder joint 180 is pulled by the driving force due to the tension of the twisted cord 132 in the direction towards the motor 102. Therefore, the twisting cord has a function of converting rotational movement (from the torque of the motor) into linear movement (from the tension caused by the twisted cords). In addition, if the rotation of the shaft 102B of the motor 102 rotates reversely, the twisted cords 132 is loosened. As a result the shoulder joint 180 moves in direction away from the motor with the aid of the force generated by the spring assembly 152 so as to increasing the length of the cord 132. The length of the cord 132 becomes the maximum value L when they are in the loosened state. It will be appreciated that motor 102 need not actively operate in the opposition direction; but that once the cords are wound they will naturally unwind when the motor is not in operation. This passive action can be enhanced if the motor arrangement is such that the motor for winding one of the cords of a pair causes the other one of the cords of the pair to unwind. The same or similar arrangement is preferably provided for the motor 104, 106 and 108 and cord 134, 136 and 138 respectively. Figure 3B illustrates schematically the actuation portion 200 of the robotic arm 10 at a second position in use. The motor 106 consists of a rotating output shaft 106B, comprising a coupling 116. The cord 136 is looped around the coupling 1 16 on one end and then connected to the hinged lever member 166 about the shoulder joint 180 by a secured connection means 306. Rotation of the shaft 106B of the motor 106 results in the twisting or winding of the cord 136. Twisting of cords results in length of the cord 136 being shortened and as a result, the shoulder joint 180 is pulled by the driving force due to the tension of the twisted cord 136 in the direction towards the motor 106. Although the robot arm 10 is described to comprise sequentially four motors and four twisted cords arranged in pairs, it will be appreciated that alternative motor and cord arrangements may be used. Furthermore, it will also be appreciated that fewer or more then the stated number of motors and cords may be used to achieve the desired output. The motors may work in concert to provide flexion on extension of the arm to result in the degrees of motions of an arm substantially emulating those of a human arm.

With accurate selection of the motor, cord diameter and cord length, the hinged lever member's dynamics may be tailored to perform various specified functions. Advantageously, the combination creates a low inertia and resilient actuator.

Figure 4 illustrates a side perspective of the components of the robotic arm 10. The motors 106 and 108 are depicted whereby cord 136 connects the motor shaft 106B to the lever 166 and cord 138 connects the motor shaft 108B to the lever 168 in an antagonistic fashion. Rotation of the shaft 106B results in shortening of the cord 136 and the pulling of the lever 166. The lever 166 is directly attached to a shaft (not illustrated). The shaft is attached to the upper arm 182. Actuation of the twisted cord 136 results in extension of the upper arm, and the actuation of the twisted cord 138 results in flexion of the upper arm. Rotation of the shaft 108B results in shortening of the cord 138 and the pulling of the lever 168 towards the motor 108 against the force of the spring assembly 152, which through careful matching does not exert any significant force on the cord 138.

Figure 5 illustrates a top perspective of the components of the robotic arm and provides sequential arrangement of the motor portion 12. The elbow joint 184 may be actuated in the same manner as described above with the addition that the hinged lever member 160 is connected (at a small offset) through a shaft to a bar 400 as illustrated in Figure 5. This bar 400 is contained within the upper-arm portion 182 and its end is connected to the fore-arm portion 186 at a small off-set to the elbow joint 184 and causes the fore-arm portion 186 to move when the shaft to which lever 168 is attached. Alternatively, the elbow joint 184 may be actuated using a sliding mechanism. Figure 6A-6B illustrates schematically the motor portion 12 of the robotic arm 10. Motor 106 has been illustrates in figures 6A -6B however it will be appreciated that motors 102, 104 and 108 may comprise the same components and provide similar functionality to motor 106.

As illustrated, the motor 106 is encased in motor housing 106B by a slideable mechanism allowing for motor 106 to move between a first and second position in respect of motor housing 106B. The motor 106 is attached to housing 106B via a casing 106C which in this example caps one of the faces of the motor 106. Casing 106C slidably attaches to housing 106B via two cylindrical protrusions or pins 106D, 106E. Housing 106B comprises three apertures or openings, shaped and arranged so as to allow motor shaft 106B and pins 106D, 106E to be inserted there through. Pins 106D, 106E may further comprise, as illustrated, spring assembly 196 which cushion the movement of the motor 106 between said first and second positions. It will be appreciated that the casing 106C may have different dimensions and attach to motor 106 and/or housing 106B in a different manner.

This arrangement is such that when the motor is in use, shaft 106B causes the cord 136 (not illustrated) to twist or wind thereby shortening the length between the motor 106 and the object being actuated. By allowing the motor 106 to move between a first or rested non- active, position and a second position where the cord is wound, the motor 106 follows the movement of the cord by a predetermined distance which reduces the chance for the cord 136 to snap at the shaft connection and generally places less strain on the cord 136 in use. Additionally, by allowing the shoulder to move between a first and second position, the movement of the moveable joint more closely emulates the action of the human shoulder. In this invention the motor 106 is the type in which the spring assembly 195 has a known incremental sensor comprising of a resistance wire thus providing feedback for force.

Although not depicted in the figures, the motor source may be geared with a gearbox (not illustrated). As will be understood by those in the field of actuator design, such a gear box may be integral to the motor source and in any case is not required for all applications.

Those skilled in the art will appreciate that while the forgoing has described what is considered to be the best mode and, where appropriate, other modes of performing the invention should not be limited to the specific configurations and methods disclosed in this description of the preferred embodiment. Those skilled in the art will recognize that the invention has a broad range of applications in many different types of robotics and that the embodiments may take a wide range of modifications without departing from the inventive concept as defined in the appended claims.

Claims

1. A linear actuation mechanism for robots and related devices, comprising:

a one degree of freedom rotating joint moveable between a first and a second position;

at least one cord attached to said one degree of freedom rotating joint;

means for rotating the at least one cord; and

a biasing assembly arranged so as to counterbalance the load acting on said one degree of freedom rotating joint,

wherein actuation of the means for rotating twists or winds the cord causing the one degree of freedom rotating joint to move from the first to a second position.

2. The linear actuation mechanism of claim 1 ,

wherein at least one cord comprises a plurality of cords attached to said one degree of freedom rotating joint;

wherein the cords are arranged as a agonist/antagonist pair, such that actuating the first cord rotates said one degree of freedom rotating joint from the first to the second position and actuating a second cord rotates said one degree of freedom rotating joint from the second to the first position.

3. The linear actuation mechanism of claim 1 or claim 2, wherein the means for rotating the at least one cord comprises a motor assembly.

4. The linear actuation mechanism of claim 3, wherein the motor assembly comprises one motor for each cord.

5. The linear actuation mechanism of claim 4, wherein the linear actuating mechanism comprises four cords and four means for rotating said cords.

6. The linear actuation mechanism of any preceding claim, wherein the biasing assembly comprises one or more springs attached to said one degree of freedom rotating joint.

7. The linear actuation mechanism of any preceding claim, wherein the at least one cord attached to one or more hinged lever members provided on said one degree of freedom rotating joint.

8. A motor assembly for use with the linear actuating mechanism of any proceeding claims, comprising: a motor housing; and

a motor mounted so as to be moveable between a first and a second position in respect of the housing,

wherein the motor moves from the first to the second position in use.

9. The motor assembly of claim 8, wherein the motor is seated in a casing which is moveable with respect to the housing such that is use, the casing is moved in the axis of the load applied against a bias between the casing and the housing.

10. The motor assembly of claim 9, wherein the casing comprises pins arranged to cooperate with in apertures in the housing.

1 1 . The motor assembly of claim 10, wherein the casing further comprises springs arranged around the pins.

12. The motor assembly of any of claims 8 to 1 1 , wherein the motor moves between the first position to the second position as a result of the motor being pulled by the linear actuating mechanism in use.

13. A kit assembly for use with the linear actuating mechanism of any claims 1-7, wherein the kit comprises one or more biasing assemblies.

14. A kit assembly for use with the linear actuating mechanism of claim 13, wherein the biasing assemblies are adapted such that the biasing means are easily replaceable and or interchangeable and or detachable and or adjustable into the robotic arm.

15 A kit assembly for use with the linear actuating mechanism of any claims 1-7, wherein the kit comprises one or more cord assemblies.

16. A kit assembly for use with the linear actuating mechanism of claim 15, wherein a cord of the cord assemblies is adapted to be user interchangeable and or detachable and or easily adjustable and or replaceable into the robotic arm.

17. A robotic arm comprising the linear actuating mechanism of any of claims 1 to 7 and/or optionally the motor assembly of any of claims 8 to 12.

18. A linear actuating mechanism and/or optionally a motor assembly and/or optionally a robotic arm substantially as hereinbefore described with reference to the accompanying drawings.