DESC:FIELD OF THE INVENTION
The present invention relates to a modular serial-chain robot.
More specifically, the present invention relates to a set of modular components that can be deployed in different ways to obtain a physical prototype of a robotic arm with any architecture that is physically feasible, thereby enabling effective understanding of the concepts related to robotics.

BACKGROUND OF THE INVENTION
A serial-chain robot is a type of robotic arm that consists of a series of connected links, each of which can rotate around an axis. These robots are widely used in industry for tasks such as assembly, welding, painting, and material handling, among others. A Serial-chain robot’s components can be designed to have a modular architecture. The term "modular" refers to the fact that the robot is composed of interchangeable parts or modules that can be deployed in different ways to create different robotic arm configurations. This allows for flexibility in design and the ability to adapt to different applications.
Serial-chain robots are classified based on the number of degrees-of-freedom (DOF) they possess, which refers to the number of independent motions that can be performed by the robotic arm.
Serial-chain robots are widely used in various industries to execute tasks that are performed by a human, which are monotonous and repetitive. The design and control of serial-chain robots are complex, that involves concepts from mechanical engineering, electrical engineering, and computer science. The robot arm's motion planning and control are essential to ensure that it can perform its intended tasks accurately and safely.
Due to the growing importance of robotics in engineering education, it has become essential to teach students the architecture of serial-chain robots along with the relationship between input and output motions. There has been a growing interest in using modular serial-chain robots in education to teach robotics concepts to students.
Reference is made to Patent application CN104269099A titled “Modularized building-block-type demountable serial robot” which discloses modularized building-block-type demountable serial robot comprising an experiment working table, a modularized building-block-type demountable serial robot body, a workpiece support and a control computer are arranged on the experiment working table, and the modularized building-block-type demountable serial robot body comprises a first joint module, a second joint module, a third joint module, a fourth joint module, a fifth joint module, a sixth joint module and a robot tail end tool which are sequentially arranged and detachable if needed. A student is made to disassemble, assemble and combine the robot and understand the joint structure, the principle and components of the serial robot to grasp its composition, functions and the different control methods of the electromechanical system, the operational ability of the robotic arm. This can help in fostering the innovation and development ability of the students.
Another reference is made to Patent application CN204315156U titled “The dismantled and assembled serial manipulator of a kind of modular building block type” which discloses dismantled and assembled serial manipulator. A kind of modular building block type comprising of a laboratory bench provided with the dismantled and assembled serial chain robotic arm of modular building block type, work support and computer for controlling the dismantled and assembled serial machine human body of modular building block type. It allows students to take action on one's own dismounting assembly robot, understand serial manipulator articulation structure, principles and components and parts composition, thus grasp the composition of serial manipulator Mechatronic control system, function and control method, training student manipulative ability and innovative development ability.
However, the modular robotic models in the existing state of art are very complex and time consuming to assemble and dismantle and can be only used for one specific application. The existing technologies with modular architecture are expensive which limits the scope of that product in the educational field. Further, the Denavit-Hartenberg (DH) parameters cannot be altered according to the user's / student’s requirements.
The present invention provides a modular serial-chain robot with plug-and-play architecture with a universal adapter which aims to address the challenges faced in teaching and learning robotics by providing a modular, easy to deploy and dismantle serial chain robot. The ability to deploy and dismantle the robotic arm using modular components where DH variables can be altered as per the requirement allows the students to learn the underlying principles of robotics in a hands-on and interactive way.

ADVANTAGES OF THE PRESENT INVENTION OVER THE EXISTING STATE OF ART:
The present invention provides several advantages and improvements over existing state of art.
Firstly, the components of the present invention can be connected to obtain any serial-chain robotic arm for any given Denavit-Hartenberg (DH) parameters. The DH parameters define the geometry of how each robot link attaches to its previous or adjoining link via a joint.
The assembling procedure of the modular components or units of the present invention enable the user to learn the concepts related to robotics in an effective manner. This can be attributed to the plug-and-play feature with the do-it-yourself (DIY) approach of the invention. The present invention allows the user to dismantle the assembly any number of times so that a different or same robotic arm can again be constructed.
The present invention allows the teacher to explain several robotic architectures in a class or lab session and evaluation of the students can also be conducted by giving any valid architecture for the students to build, which is not possible in any robotic arm in existing state of art.
Besides robotics education, the present invention can be integrated with robotics learning and simulation software so that a virtual prototype developed in the software can be developed as a physical prototype. This integration would allow for a seamless teaching and learning experience.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a modular serial-chain robot with plug-and-play architecture, which enables the user to learn the concepts related to robotics in an effective manner through a do-it-yourself (DIY) approach.
Another object of the present invention is to provide a modular serial-chain robot that can be constructed using modular components which can be easily deployed or dismantled, enabling users to build different types of robotic arms based on their specific requirements.
Yet another object of the present invention is to provide a modular serial-chain robot that can be used for educational purposes, allowing users to understand the concepts related to robotic arm architecture and the relationship between input and output motions.
Yet another object of the present invention is to provide a modular serial chain robot which can be customized according to the user's need as per the given DH parameters, allowing for greater flexibility in design and operation.
Yet another object of the present invention is to provide a modular serial-chain robot that can be used for finding the DH parameters of the model which is generated with the modular components.
Yet another object of the present invention is to provide a modular serial-chain robot that can be easily replicated, enabling the user to build multiple robotic arms for educational, research, or commercial purposes.
Yet another object of the present invention is to provide a platform or a base on which integration with robotic learning and simulation software can be done allowing users to develop virtual prototypes that can later be converted into physical models.

SUMMARY OF THE INVENTION:
The present invention is directed to a modular serial-chain robot which introduces a set of modular components that can be deployed to create a physical prototype of a robotic arm. These sets of modular components can be deployed in different ways to obtain a physical prototype of a robotic arm with any architecture that is physically feasible, thereby enabling effective understanding of the concepts related to robotics.
The modular serial-chain robot comprises of several components including modular link, adapter, motor, and clamp, which can be deployed in various configurations depending on the need of the user. The robot has several modular links that can be deployed together to create the robot arm. The links can be provided with their length as several standard values so that the user can choose them as per the requirements. The adapter is an important part of the robot. It connects the motor to the link(s) and has holes on five of its faces. It can be oriented in different ways to obtain the required architecture of the robot arm. The adapter has to be connected with a motor and link(s) using screws or a similar arrangement. The robot uses rotary motors as joint actuators. These motors are connected to the motor adapter to create the robotic arm. Clamps are used to connect the components together and are used to hold the links, motor, and adapter in place, thus creating a stable and balanced structure.
The components of the present invention can be connected to form any of the three possibilities of adjacent joint axes, namely, parallel, intersecting or skew. The links can be provided with their length as several standard values, allowing the user to choose according to their requirements. The adapter directly connects to a motor and has holes on five of its faces, allowing for the connection between neighbouring links through the joint (motor) to be made to obtain the required architecture of the robot arm. The adapter is connected with a motor and link(s) using screws or similar arrangement and motor can also be used as a part of the link in certain embodiments. In other embodiments, the clamp is also used to connect the components together. These components can be connected to form serial-chain based robotic arm for any given Denavit-Hartenberg (DH) parameters as per the requirement of the user.
The novelty of the invention lies in the way the modular components have been designed such that they can be easily deployed and dismantled to obtain a serial robot with any architecture that is physically feasible. Therefore, by using the components in different ways, several serial-chain based robotic arms can be made as physical prototypes. Once these prototypes are developed, the motion planning and executing of tasks by the given robot can be implemented and tested.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1(a) and 1(b) depicts the architecture of a serial robot and its exploded view.
Figure 2(a) depicts the motor illustrating the motor’s shaft disc which is its axis of rotation.
Figure 2(b) depicts the clamp.
Figure 2(c) and Figure 2(d) depicts the adapter.
Figure 2(c) depicts the adapter as a hollow cube, missing one face.
Figure 2(d) depicts the adapter with one of its side faces having holes at an offset.
Figure 2(e) and Figure 2(f) depict the links of the robot.
Figure 2(e) depicts the straight link in three default lengths,
Figure 2(f) depicts the U-shaped link which is crucial for a spherical wrist configuration.
Figure 3(a) depicts the sub-assembly components for the parallel axes configuration and lays out the units and how they fit together to form a parallel joint axis.
Figure 3(b) depicts the parallel axes sub-assembly showing two parallel joint axes, as an exploded view.
Figure 4(a-b) depicts the intersecting axes sub-assembly, where consecutive joint axes intersect at a point.
Figure 4(c-d) depicts the skewed axes sub-assembly, where joint axes are neither parallel nor intersecting.
Figure 5(a-b) depicts the spherical wrist sub-assembly showcasing the three consecutive axes intersecting at the wrist point.
Figure 6(a) depicts the steps of the Robot Arm Model Generator (RAMG) methodology in a flowchart format, with DH parameters as input.
Figure 6(b) depicts a detailed flowchart depicting the Iterative Program function/method of the RAMG.
Figure 7(a-b) depicts prototypes of the planar 2R and 3R manipulators (R: Revolute joint).
Figure 8(a-b) depicts the virtual models of a 6-axes spherical manipulator and an offset wrist manipulator.
DETAILED DESCRIPTION OF THE INVENTION ILLUSTRATIONS AND EXAMPLES
While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of “a”, “an”, and “the” include plural references. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.

Modular serial-chain robot comprises of a set of building blocks that can be connected to obtain the system. Reconfiguration of a robotic system can be divided into 3 categories. The first category comprises of robots which can self-configure to any desired architecture. The second category has robots that can be reconfigured with relative ease by a person with amateur or intermediate level of expertise. The last category deals with robots which need experts to reconfigure the manipulator.
UNITS
Four basic components of the present invention are as follows:
Motor: It is an actuator which rotates to the required orientation based on the command received from its controller. This corresponds to the joint angle (?) defined as one of the DH parameters. In the present invention, Dynamixel AX-12A servo motors have been considered. However, based on the requirements, other motors can be suitably included. In a serial manipulator with only revolute joints, the number of servo motors is same as the number of joint axes, i.e., DOF of the manipulator. Referring to Figure 2(a), the motor’s CAD model shows the motor’s shaft disc which is along its axis of rotation.

Clamp: It is a readily available component that is supplied with Dynamixel motors and is shown in Figure 2(b). It is fastened at the base face of a motor and has provision to connect to other components.

Adapter: It is a custom designed component in the shape of a hollow cube with one of its faces missing. The face opposite to the missing face is referred to as base face. All other faces are categorized as transverse faces, as illustrated in Figure 2(c). The adapter is fastened to the shaft disc using screws. The adapter can be mounted such that either its base face or one of its transverse faces are connected to the shaft disc. In a few instances, certain offset is expected for the holes of screws on the transverse faces, as illustrated in Figure 2(d). The adapters are used to connect links and allow the user to build the prototype considering the twist angle (a), another DH parameter.

Link: It is a rigid body which correspond to the joint offset (b) and link length (a), the remaining two DH parameters. For intermediate joints, these links are inserted into the open faces of two adapters and fastened to them. The last link has only one adapter and the farther end of the link can be fitted with an end-effector tool. Note that in a few instances, two adapters are also connected with each other whenever necessary. The straight link, shown in Figure 2(e) has three default length to choose from. As a special arrangement of these links, one can also obtain a U-shaped link, shown in Figure 2(f), which is required in a spherical wrist configuration.

SUB-ASSEMBLIES
The sub-assemblies are the building blocks for assembling the virtual and physical prototypes of a serial-manipulator for its given DH parameters. These sub-assemblies have three types of relationships with respect to the joint axes present in them, namely, parallel axes, intersecting axes, and skewed axes. These are based on the relative distance and angle between two consecutive joint axes. As a special case, a spherical wrist that is found in majority of the 6-axes serial manipulators is also considered as a sub-assembly. The construction of these four sub-assemblies using the modular units introduced is provided below:

Parallel axes: The required modular units for the parallel axes are shown in Figure 3(a), which is an exploded view of the sub-assembly. The modular units are taken from Figure 2 and are assembled by positioning and orienting each unit in an arrangement that allows two parallel joint axes, as shown in Figure 3(b). The relative distance between the joint axes is the link length (a). The joint offset (b) is zero in this case and the twist angle (a) is either 0? or 180?. The fourth parameter, i.e., joint angle (?) varies as per the rotation of the motor corresponding to the first motor.

Intersecting axes: Referring to Figure 4 (a-b), the consecutive joint axes intersect at a point. Based on the DH parameter convention, joint offset (b) is shown as a positive value, the link length (a) is zero and the twist angle (a) is either 90? or 270?.

Skewed axes: In this type of configuration, the joint axes are neither parallel nor intersecting. Hence both the joint axes are skewed to each other. The connected and exploded sub-assembly for this case are shown in Figures 4(c-d), where the joint offset b is considered as zero. Suitable changes can be made so that a scenario with positive value of b can be assembled.

Spherical wrist: A spherical wrist has three consecutive axes intersecting at a point referred to as wrist point. This configuration follows one of Pieper’s criteria. Virtual and physical prototypes of a spherical wrist are shown in Figure 5, where wrist link is used to obtain the common intersection point.
Prismatic Joints
Linear actuators corresponding to the prismatic joints can be used by connecting the ends of the actuator using two adapters, as done for a revolute joint, which is another possibility of the proposed modular architecture.
Robot Arm Model Generator (RAMG)
The individual sub-assemblies are connected with each other based on certain rules. These generate models of the manipulator for a given architecture, as per its DH parameters. Here, the methodology of forward iteration from the base link to the end-effector is presented as Robot Arm Model Generator (RAMG). A flowchart with the main steps of RAMG is shown in Figure 6(a), where the DH parameters are considered as input. Based on the number of joint axes n, i.e., the number of rows in the DH parameter table, a condition to check for existence of a spherical wrist is executed. In all the possible scenarios, a set of procedures in Iterative Program function or method is executed. The Iterative Program has a flowchart shown in Figure 6(b), which corresponds to ith row of DH parameters, where the conditions for the DH parameters of the corresponding row are checked and classified as parallel, intersecting, or skewed axes. Accordingly, the sub-assembly is connected to the previously developed model in the current step of iteration. In case of a spherical wrist scenario, the sub-assembly for the spherical wrist is connected to the last iteration model. RAMG methodology is used to generate models first as virtual prototypes and later can be developed as physical prototypes.
Planar 2R Manipulator
A 2R manipulator is a robotic arm which consists of two joint axes or two DOFs, where R represents a revolute joint. In the case of a planar 2R manipulator, its two joint axes are parallel to each other. It is generally used to control the position of its end-effector tip to perform some tasks. The virtual prototype developed using RAMG methodology is shown in Figures 7(a).
Planar 3R Manipulator
An extension of the planar 2R manipulator with another parallel-axes sub-assembly results in a planar 3R manipulator shown in Figures 7(b). This is another type of planar manipulator in which there are three joint axes or DOF’s. This manipular is similar to the above mentioned 2R manipulator, the only difference being the number of joint axes or degrees of Freedoms (DOF).
Spherical Wrist Manipulator with 6-DOF
The DH parameters of a 6-axes spherical manipulator have to satisfy certain conditions. The first and second joint axes can be either intersecting or skewed. The second and third joint axes are parallel. The third and fourth axes can be intersecting or skewed. The fourth, fifth and sixth axes should intersect at a point. These DH parameters are used to generate the virtual model as shown in Figure 8(a).
Offset Wrist Manipulator with 6-DOF
Here, the difference from the spherical wrist manipulator is that the second through fourth axes are parallel to each other. The last three axes do not intersect. This satisfies Pieper’s condition to obtain analytical solution for inverse kinematics. An example of DH parameters set satisfying these conditions are used to generate a virtual model is shown in Figure 8(b). This configuration is similar to the UR10 manipulator and other similar variants from Universal Robots.
Tools for Robotics Education
There are various tools available for effective robotic education, which are software or hardware based. The software-based tools graphically generate 3-dimensional models of a robot and offer features to program, simulate and build algorithms for motion planning and path planning. Software like RoboAnalyzer are designed specifically to teach kinematics of robots to students. It allows the users to generate robot manipulators of the required configuration by manually selecting the type and entering the DH parameters. It displays the coordinate frames corresponding to each joint axis and displays the numerical values associated with HTMs (HTM: Homogenous Transformation Matrix) associated with each row of the DH table. There are a few pre-loaded CAD models of robots that students can simulate by jogging in joint-and-Cartesian space, thereby understanding the corresponding motion.
RoboDK is a software that is used in academia and industry to simulate industrial robots. It offers a wide range of industrial robots of different companies to choose from, as per the requirement. It also suggests robots which can be selected according to the reach, payload, type of robot configuration, DOF, weight, etc. Users can simulate, test and program robots using this tool. Robotics Toolbox for MATLAB provides basic functions that allow users to learn robotics concepts such as forward and inverse kinematics, motion planning, etc., by writing MATLAB code on top of the Robotics Toolbox. CoppeliaSim, previously known as V-REP, is another robot simulation software, which allows modeling and analysis of serial, parallel, legged and wheeled mobile robots.

The physical prototypes of serial manipulators are available in standard assembled form, which are supplied by the robot manufacturers. These are also available as DIY (Do-it-yourself) kits where components of the robot are included in a package and the user has to assemble the prototype by following the guidelines in a manual provided by the manufacturers. These kits provide a good exposure to learn the concepts related to robot architecture. However, since the architecture cannot be changed and the dismantling and re-assembling is usually not supported, the learning is short lived. Hence, there exists a need for modular robots, which can be assembled and dismantled and again assembled depending on the user's needs.
,CLAIMS:1. A modular serial-chain robot (100) comprising:
? a plurality of modular links (101) of varied selectable lengths;
? a plurality of rotary motors (102) configured to actuate joints,
? at least one adapter (103) configured to connect said rotary motor (102) with said modular link (101);
? a plurality of clamps (104) to securely interconnect said modular links (101), rotary motors (102), and adapter (103);
wherein, said modular serial-chain robot (100)
? is capable of being configured into varied physically feasible architecture based on any given Denavit-Hartenberg (DH) parameters,
? is capable of being constructed using a plug-and-play architecture,
thereby enabling technical comprehension of robot kinematics, dynamics, and the significance of DH parameters in robotic construction.
2. The modular serial-chain robot (100) as claimed in claim 1, wherein said adapter (103) comprises of holes on at least five of its faces such that said adapter is capable of being oriented in multiple ways to achieve a desired architecture.
3. The modular serial-chain robot (100) as claimed in claim 1, wherein said modular serial chain robot (100) is configured to facilitate a hands-on do-it-yourself (DIY) approach, thereby providing multiple assembly, disassembly and reconfiguration of the robotic structure.
4. The modular serial-chain robot (100) as claimed in claim 1, wherein said modular links (101) are interconnected to form parallel, intersecting, or skewed configurations of adjacent joint axes based on user requirements.
5. The modular serial-chain robot (100) as claimed in claim 1, further comprises of a U-shaped link (105) providing a spherical wrist configuration using a unique combination of said modular links (101), thereby enabling three consecutive joint axes to intersect at a common point.
6. The modular serial-chain robot (100) as claimed in claim 1, wherein said serial chain robot (100) is capable of transitioning seamlessly between virtual models in robotics simulation software and physical prototypes.
7. A method of constructing the modular serial-chain robot (100) using Robot Arm Model Generator (RAMG) methodology, comprising the steps of:
? determining a desired robot architecture defined by specific Denavit-Hartenberg (DH) parameters;
? selecting modular links (101) of desired length;
? connecting rotary motors (102) to the selected modular links (101) via adapters (103) and clamps (104)
? configuring the serial-chain robot (100) based on determined DH parameters, resulting in a physical prototype reflecting the desired architecture,
wherein said modular serial-chain robot (100) is being configured to form any one of parallel, intersecting, skew joint axes configurations between adjacent joint axes or a spherical wrist configuration.
8. The method of constructing a modular serial-chain robot (100) as claimed in claim 7, wherein said Robot Arm Model Generator (RAMG) methodology comprising the steps of:
? determining desired Denavit-Hartenberg (DH) parameters;
? selecting and connecting modular units based on said DH parameters to form sub-assemblies reflecting joint axis relationships;
? assembling said sub-assemblies in sequence to create said modular serial-chain robot (100) reflecting the defined DH parameters.
9. The method of constructing a modular serial-chain robot (100) as claimed in claim 7, wherein said Robot Arm Model Generator (RAMG) methodology uses DH parameters to facilitate the construction of virtual and physical prototypes of the modular serial-chain robot (100) thereby enabling technical comprehension of robot kinematics, dynamics, and the significance of DH parameters in robot construction.