DESC:
FIELD OF THE INVENTION:
This invention relates to the field of electronics engineering and robotics.

Particularly, this invention relates to a non-conventional calibration system for industrial robots.

BACKGROUND OF THE INVENTION:
An industrial robot is a robot system used for production, manufacturing, and service industries. Industrial robots are programmable, automated, and are able to move on three or more axes in space. There are many applications of industrial robots with repetitive actions, which include picking and placing, manufacturing goods inspection, welding, and painting, labeling, and testing. With these repetitive requirements robots need to be verified and calibrated with a certain interval of time through standard verification systems. Robot calibration is an integrated process of measurement of performance parameter and confirmation of those with a feedback from robot system.

Static calibration is an identification of those parameters which influence mainly static positioning characteristics of a robot (position and orientation of the end-effector), while dynamic calibration is used to identify parameters influencing primarily motion characteristics (velocity and forces).

When a robot is to be calibrated, it is very important to check if the kinematic model of the off-line program is exactly the same as the robot control unit, since operation manuals from manufacturers do not always inform precise geometric parameter values.

There are defined International Standards which describe methods of specifying and testing at least the following performance characteristics of manipulating industrial robots as:
1. Pose accuracy and Pose repeatability: Differences which occur between a command and attained pose, and fluctuations in the attained pose for a series of repeat visits to a command pose;
2. Multi-directional pose accuracy variation: Deviation between the different mean attained poses achieved when visiting the same command pose n times from three orthogonal directions;
3. Distance accuracy and distance repeatability: Deviation which occurs in the distance between two command poses and two sets of mean attained poses, and the fluctuations in distances for a series of repeat movements between the two poses;
4. Path accuracy and path repeatability: Independent of the shape of the command path.

Other listed parameters are related to time of response, smoothness of motions, and the like. Repeatability is one of the main measurable characteristics in terms of evaluated path, position and orientation called as pose. These are the parameters to be ensured for achieving every time the robot has to be set up and the motion of the end effector.

There is a direct impact on the effectiveness of a robot when it is calibrated.

All robot manufacturers, typically, mention, in their information site, about their robot specification data, but a robot user does not know optimal conditions under which it has to be operated and those which are acceptable. For example, the specification mentioned on industrial robot ABB 1520ID is listed as ±0.35mm repeatability, 1000mm/s speed, and 4kg payload (kept in the slot 14a). However, through this information, it is not understood by a user about the mentioned repeatability at a known speed and a stated payload capacity. With such information in industrial robot process parameters, few or no standard is present in any robot manufacturing industries. So, it is not clear for a robot user to understand effects or that significance of the parameters in some reference is unimportant.

Therefore, it is very much important to examine the interface among the various robot parameters and determine optimum conditions under which a given mix of values can be obtained. All these optimal parameters considerations lead to improved design and deployment of industrial robots. However, there is an unavailability of guidelines or standards to develop in-house calibration procedures and to use specific meteorological gauges.

Furthermore, Industrial robot applications have been exponentially rise since the inception of robots. An industrial robot is a robot system used for production, manufacturing and service industries. There are many significant applications where robots need to be accurate and repeatable. Accuracy is a degree of closeness of the actual value to the set value or target value. Repeatability is a capacity of a robot to visit a taught position again and again.

Therefore, with such repetitive requirements, robots need to be verified and calibrated with a certain interval of time.

OBJECTS OF THE INVENTION:
An object of the invention is to calibrate robots, at discrete time intervals, in order to ensure their accurate repeatability.

SUMMARY OF THE INVENTION:
According to this invention, there is provided an industrial robot calibration system, configured to calibrate a robot, said system comprises:
- an elongate bar configured to be coupled to said robot that is to be calibrated;
- a base plate with adjustable height mechanism, said base plate configured to receive, and hold, said elongate bar, centrally, said elongate bar, upon receipt at said system, protruding in a z-direction out of an x-y plane of said base plate, said base plate comprising a sensor, at a location, which receives said elongate bar from said robot;
- said base plate holding a first sliding rail, atop said base plate, configured to host a first LVDT sensor, at its end which interfaces with said elongate bar;
- said base plate holding a second sliding rail, atop said base plate, configured to host a second LVDT sensor, at its end which interfaces with said elongate bar;
- said base plate holding a third sliding rail, atop said base plate, configured to host a third LVDT sensor, at its end which interfaces with said elongate bar; and
- said base plate holding a fourth sliding rail, atop said base plate, configured to host a fourth LVDT sensor, at its end which interfaces with said elongate bar.

In at least an embodiment, said first sliding rail is positioned, offset with respect to said elongate bar, such that said corresponding sensor is tangential, establishing point contact, to an outer circumference of said elongate bar when received at said base plate.

In at least an embodiment, said second sliding rail = is positioned, offset with respect to said elongate bar, such that said corresponding sensor is tangential, establishing point contact, to an outer circumference of said elongate bar when received at said base plate.

In at least an embodiment, said third sliding rail is positioned, offset with respect to said elongate bar, such that said corresponding sensor is tangential, establishing point contact, to an outer circumference of said elongate bar when received at said base plate.

In at least an embodiment, said fourth sliding rail is positioned, offset with respect to said elongate bar, such that said corresponding sensor is tangential, establishing point contact, to an outer circumference of said elongate bar when received at said base plate.

In at least an embodiment, said elongate bar is a hollow elongate bar with weights that can be added in the hollow segment of said metallic bar.

In at least an embodiment, said elongate bar elongate bar comprising:
- a base plate which allows it to couple to said robot;
- a first elongate element protruding operatively vertically, downwards from an underside of said base plate; and
- a stub element, coaxial to said first elongate element, protruding, operatively vertically, further downwards from a farther end of said first elongate element; said stub element configured to interface with said system’s base plate when said robot moves towards said; thereby, establishing contact with relevant sensors to sense angular displacement, linear displacement, and / or effect of weight and / or velocity of said robot.

In at least an embodiment, said elongate bar is configured to:
- swivel, angularly, about its pivot point where it interfaces with said base plate; and
- move, axially, operatively upwards and operatively downwards, through its pivot point where it interfaces with said base plate.

In at least an embodiment, each of said sensors are on a locus of points equidistant from a centre, said centre being defined as a point where said first elongate arm rests on said base plate.

In at least an embodiment, said first sensor and the third sensor are collinearly aligned.

In at least an embodiment, said second sensor and the fourth sensor are collinearly aligned.

In at least an embodiment, each sensor is angularly displaced by an adjacent sensor by an angle of 90 degrees.

In at least an embodiment, each of said sensors is linked on to said corresponding sliding elements with resilient mechanisms such that said resilient mechanism’s naturally resting position leads to said sensor touching said elongate rod and upon action of forces, its resilient forces compress, displace said sensor, leading to sensing and recording values of said sensor, and leading said sensor back to its naturally interfacing tangential position.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:

Figure1 illustrates a front view of the setup of this system;
Figure 2 illustrates a top view of the setup of this system;
Figure 3 illustrates a LVDT and Adjustable Table arrangement;
Figure 4 illustrates set-up details for LVDT and Adjustable Table arrangement;
Figure 4a illustrates the elongate bar with its constituent members;
Figure 5 illustrates a robot, that is to be calibrated, using the system (as seen in Figures 1, 2, 3, and 4) of this invention;
Figure 6 illustrates a flowchart depicting an algorithm for calibration / measurement; using the system of this invention; and
Figure 7 illustrates the factors, their levels, and their interactions using an application of Taguchi L27 orthogonal array method in order to validate the result of calibration, according to the system and method of this invention

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided an industrial robot calibration system.

Figure1 illustrates a front view of the setup of this system.
Figure 3 illustrates a top view of the setup of this system.
Figure 3 illustrates a LVDT and Adjustable Table arrangement.
Figure 4 illustrates set-up details for LVDT and Adjustable Table arrangement.
Figure 5 illustrates a robot (10), that is to be calibrated, using the system (as seen in Figures 1, 2, 3, and 4) of this invention.

In at least an embodiment, this system comprises a flat table / base plate (12) with adjustable height mechanism. Adjustment in height is done depending on experimental requirement.

In at least an embodiment, the base plate (12) is configured to hold a substantially centrally located elongate bar (14), also called as a mastering bar, which protrudes in a z-direction out of the x-y plane of the base plate. The elongate bar (14) comprises an LVDT sensor, at its operative bottom, to sense displacement due to load.

In some embodiments, the elongate bar (14), i.e. the mastering bar, is configured to be attached to a wrist of a robot (10) that is to be calibrated. In at least an embodiment, the elongate bar is a hollow (14a) elongate bar with weights that can be added in the hollow segment of the metallic bar.

Figure 4a illustrates the elongate bar (14) with its constituent members.

In at least an embodiment, the elongate bar (14) comprises a base plate (14b) which allows it to hook / attach to a robotic arm / wrist (10). A first elongate element (14a) protrudes operatively vertically, downwards from the underside of the base plate (14b). A further stub element (14c), coaxial to the first elongate element (14a), protrudes, operatively vertically, further downwards from the farther end of the first elongate element (14a); this stub element (14c), eventually, interfaces with the base plate (12) when the robot (10) moves towards the system of this invention; thereby establishing contact with relevant sensors to sense angular displacement, linear displacement, and / or effect of weight and / or velocity of the robot (10).

In some embodiment, the elongate bar (14) is configured to:
- Swivel, angularly, about its pivot point where it interfaces with the base plate (12);
- Move, axially, operatively upwards and operatively downwards, through its pivot point where it interfaces with the base plate (12).
Due to axial motion, occurring due to placement of load on the elongate bar (14), the corresponding sensor (fifth LVDT sensor) senses, and records, linear displacement in the Z-direction.

Typically, the elongate bar (14) is a metallic bar.

In at least an embodiment, the base plate (12) holds a first sliding rail (16a), atop the base plate (12), configured to host a first LVDT sensor (17a), at its end which interfaces with the elongate bar (14). The first sliding rail (16a) is positioned, offset with respect to the elongate bar (14), such that the end LVDT sensor is tangential to the outer circumference of the elongate bar (14). There is point contact between the LVDT (17a) sensor and the elongate bar (14) for avoiding error between those elements. The first sliding rail (16a) enables movement of the LVDT sensor, linearly, in an X-Y plane, thereby allowing this sensor to sense linear displacement. However, due to the tangential interfacing of the elongate bar (14) with the sliding rail (16a), swiveling angular displacement of the elongate bar (14) is converted into linear displacement of the sensor, guided by the sliding rail; thereby, sensing and recording linear displacement in the X-Y plane (i.e. in the X-direction and in the Y-direction).

In at least an embodiment, the base plate (12) holds a second sliding rail (16b), atop the base plate (12), configured to host a second LVDT sensor (17b), at its end which interfaces with the elongate bar (14). The first sliding rail (16a) is positioned, offset with respect to the elongate bar (14), such that the end LVDT sensor is tangential to the outer circumference of the elongate bar (14). There is point contact between the LVDT (17b) sensor and the elongate bar (14) for avoiding error between those elements. The second sliding rail (16b) enables movement of the LVDT sensor, linearly, in an X-Y plane, thereby allowing this sensor to sense linear displacement. However, due to the tangential interfacing of the elongate bar (14) with the sliding rail (16b), swiveling angular displacement of the elongate bar (14) is converted into linear displacement of the sensor, guided by the sliding rail; thereby, sensing and recording linear displacement in the X-Y plane (i.e. in the X-direction and in the Y-direction).

In at least an embodiment, the base plate (12) holds a third sliding rail (16c), atop the base plate (12), configured to host a third LVDT sensor (17c), at its end which interfaces with the elongate bar (14). The first sliding rail (16a) is positioned, offset with respect to the elongate bar (14), such that the end LVDT sensor is tangential to the outer circumference of the elongate bar (14). There is point contact between the LVDT (17c) sensor and the elongate bar (14) for avoiding error between those elements. The third sliding rail (16c) enables movement of the LVDT sensor, linearly, in an X-Y plane, thereby allowing this sensor to sense linear displacement. However, due to the tangential interfacing of the elongate bar (14) with the sliding rail (16c), swiveling angular displacement of the elongate bar (14) is converted into linear displacement of the sensor, guided by the sliding rail; thereby, sensing and recording linear displacement in the X-Y plane (i.e. in the X-direction and in the Y-direction).

In at least an embodiment, the base plate (12) holds a fourth sliding rail (16d), atop the base plate (12), configured to host a fourth LVDT sensor (17d), at its end which interfaces with the elongate bar (14). The first sliding rail (16a) is positioned, offset with respect to the elongate bar (14), such that the end LVDT sensor is tangential to the outer circumference of the elongate bar (14). There is point contact between the LVDT (17d) sensor and the elongate bar (14) for avoiding error between those elements. The fourth sliding rail (16d) enables movement of the LVDT sensor, linearly, in an X-Y plane, thereby allowing this sensor to sense linear displacement. However, due to the tangential interfacing of the elongate bar (14) with the sliding rail (16a), swiveling angular displacement of the elongate bar (14) is converted into linear displacement of the sensor, guided by the sliding rail; thereby, sensing and recording linear displacement in the X-Y plane (i.e. in the X-direction and in the Y-direction).

In at least an embodiment, each of the sensors (17a, 17b, 17c, 17d) are on a locus of points equidistant from the centre, the centre being defined as a point where the first elongate arm (14) rests on the system of this invention.

In at least an embodiment, the first sensor (17a) and the third sensor (17c) are collinearly aligned.

In at least an embodiment, the second sensor (17b) and the fourth sensor (17d) are collinearly aligned.

In at least an embodiment, each sensor is angularly displaced by an adjacent sensor by an angle of 90 degrees.

Each of the sensors (17a, 17b, 17c, 17d) are linked on to the corresponding sliding elements (16a, 16b, 16c, 16d) with resilient mechanisms (compression spring) such that the resilient mechanism’s naturally resting position leads to the sensor touching the elongate rod (14) and upon action of forces, the resilient forces compress, displace the sensor, leading to sensing and recording values of the sensor, and leading the sensor back to its naturally interfacing tangential position.

In other words, when the mastering bar (14) is introduced on to the system’s base plate (12) by the robot (10), the sensors (17a, 17b, 17c, 17d) displace, accordingly, on corresponding rails (16a, 16b, 16c, 16d); these displacement values are sensed and recorded. Once that is done, the mastering bar (14) is taken away by the robot (10) and the resilient mechanisms kick in to bring the sensors to their initial resting position.

In preferred embodiments, a cycle of reading comprising the action of placing the mastering bar (14) and removing the mastering bar (14) is repeated for 30 times as mentioned in ISO 9283. Offsets are detected in x, y, and z axes by sensing displacement and velocity and correlating them with weights in the mastering bar (14).

As shown in the figures, four Linear Variable Differential Transformers (LVDTs) are placed. A LVDT core is inserted into the fixture, with a space equal to the base size of the master. There is a linkage arrangement with a spring contact between the LVDTs and the fixture so that the linkages regain its original positions after each reading. The fixture design is robust so that LVDT can withstand high forces during calibration.

Further, additional means and mechanisms are required to convert information obtained through the LVDT arrangement to a formation that is useful in calibration on a real-time basis during an industrial robot motion.

Figure 6 illustrates a flowchart depicting an algorithm for calibration / measurement; using the system of this invention.

In at least an embodiment, the following steps are followed for the purposes of registering taken data in spatial posturing correction table are as follows:
The first step conducting fine posturing at predetermine positions on reference co-ordinate systems, then read coordinates (x, y, z) of adjusted tool displayed at numerical control device after it record posturing error and fine posturing coordinate.
If necessary, data sets in x-direction and y-direction then the process go forward to next step else the entire procedure should repeat until the condition comes true.
In next step, if necessary data set in Z direction then result is ready else there will be change in height in Z direction and entire procedure will repeat again until the condition comes true.

The validation results of the robot pose repeatability after calibration procedure and setting the parameters for the spatial posturing correction are thereby completed.

The flowchart, of Figure 6, shows a flow of operations of a robot’s repeatability to enhance significantly after calibration. The proposed measurement method supplied high repeatability measurement for this calibration and had some properties of correctness, effectiveness, and practical applicability.

In at least an embodiment, the following steps are followed for the purposes of calibration using the system of this invention.
Step-I: Before carrying out a spatial posturing procedure, results of calibration are registered in a control device.
Step-II: Subsequently, a predetermined posturing, in a reference coordinate system, is precisely determined. This posturing manner is identical to that of data taking at the time of calibration.
Step-III: Subsequently, coordinate values (along axes X, Y, Z) of the posturing of the adjustment tool which are displayed in a software device at the time of posturing are read.
Step-IV: The measurement repeatability of this method was gauge as sufficient based difference between the read coordinate values and the position coordinates of the fine posturing in the reference coordinate system means a posturing error. This evaluation is performed by comparing deviation between including orientation is recorded together with the coordinates of the fine posturing in the reference coordinate system.
Step-V: The above operations are repeated a required number of times for the X-directions and Y-directions.
Step-VI: In the repeated operations, the robot has to operate over their full wide workspace. Therefore, a robot predetermined posturing in step V is different from the previous posturing. If the data taking of the necessary number of sets of data in the X-direction and Y-direction is necessary (“YES” in step V).
Step-VII: If data taking in the Z-direction is necessary (“NO” in step VI), a suitable plate is place on the surface of the reference board to change the distance in Z-axis by ?Z. The above operations are repeated a required number of times for the (X, Y, Z axes) directions, a posturing error are recorded. After the data is completed (“YES” in step VI), the position coordinates of the fine posturing and the posturing error which are recorded.

Advantages:
1. The measurement setup is simple in construction as a smaller number of linkages are in used.
2. Execution of the suggested process is relatively fast, user friendly and easy to setup.
3. Additional special equipment for tracking an arrangement of intermediate point, therefore no additional equipment cost of pre-calibration setups are required.
4. This calibration setup provides accurate and reliable measurements for industrial robot calibration.

In accordance with a non-limiting exemplary embodiment, the system of this invention was used in consonance with an ABB 1520ID industrial robot which was to be calibrated. Data from the sensors, of the system, was passed on, through a data logger and homing system interface, to a computer processor. A mastering process, in accordance with the system and method of this invention, that increases positional repeatability of the robotic arm of the ABB 1520ID industrial robot was followed. Here,

Various significant factors such as Payload (kg), Velocity (mm/s ), Reach (mm), and Level (mm) were selected in the non-limiting exemplary embodiment and were chosen at various levels based on their limiting factors as shown in Table 1, below, in order to calibrate the industrial robot positional repeatability in micron meter.

TABLE 1

The first elongate element (14), which is attached at the end of the robot (10), reaches at the system, of this invention, in an operatively vertically downward direction at various velocity levels mention in table no 1.

According to the non-limiting exemplary embodiment, the robot moved in a pre-defined path, in space, according to ISO 9283. After completing homing cycle and mastering position cycle, data was stored in the data logger. After completing 30 numbers of cycles, in a workspace, the robotic arm needed to reach vertically downward, in the fixture, for calibrating itself in the workplace with the help of the system’s sensors.

Figure 7 illustrates the factors, their levels, and their interactions using an application of Taguchi L27 orthogonal array method in order to validate the result of calibration, according to the system and method of this invention.

The following observations were made:
Effect of Payload: Higher Payload levels do not necessarily lead to better robot repeatability;
Effect of Velocity: It can be seen that repeatability generally deteriorated at low velocity; the deterioration does not seem to be very significant
Effect of Reach & Level: It can be seen that repeatability deteriorated at High Reach and low Level; the deterioration does not seem to be significant.
The best Positional Repeatability: equal to 70.2711µm, was achieved when the robot was operating at payload 4kg, velocity 1500mm/s, reach 800mm and level 1050mm.

The conclusion from the aforementioned results and observations is that, the area where the robot calibration can lead to a significant positional repeatability improvement and / or cost saving opportunities depends on given operating conditions; thereby minimizing the risk of sudden failure. In other words, as long as calibration, is done for a robot in a given workspace, using the system and method of this invention, risk of sudden failure of the robot is minimized significantly.

The TECHNICAL ADVANCMENT, of this invention, lies in the following:
- This proposed system is user friendly, ease for handling. Procedure is possible with less skilled personnel. It is less time consuming, portable, less expensive/ economical, robust calibration system and often do provide an acceptable level of accuracy;
- This calibration method represents an effective and practical technique for an industrial robot calibration on test site assignments and industrial environment. It focuses on the construction of measuring system and provides a theoretical calculation of its repeatability measurement, which is confirmed by experiments carried out on a high precision measuring device in various input parameters and conditions.

While this detailed description has disclosed certain specific embodiments for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
,CLAIMS:WE CLAIM,

1. An industrial robot calibration system, configured to calibrate a robot (10), said system comprising:
- an elongate bar (14) configured to be coupled to said robot (10) that is to be calibrated;
- a base plate (12) with adjustable height mechanism, said base plate (12) configured to receive, and hold, said elongate bar (14), centrally, said elongate bar (14), upon receipt at said system, protruding in a z-direction out of an x-y plane of said base plate (12), said base plate comprising a sensor, at a location, which receives said elongate bar (14) from said robot (10);
- said base plate (12) holding a first sliding rail (16a), atop said base plate (12), configured to host a first sensor (17a), at its end which interfaces with said elongate bar (14);
- said base plate (12) holding a second sliding rail (16b), atop said base plate (12), configured to host a second sensor (17b), at its end which interfaces with said elongate bar (14);
- said base plate (12) holding a third sliding rail (16c), atop said base plate (12), configured to host a third sensor (17c), at its end which interfaces with said elongate bar (14); and
- said base plate (12) holding a fourth sliding rail (16d), atop said base plate (12), configured to host a fourth sensor (17d), at its end which interfaces with said elongate bar (14).

2. The system as claimed in claim 1 wherein, said first sliding rail (16a) is positioned, offset with respect to said elongate bar (14), such that said corresponding sensor (17a) is tangential, establishing point contact, to an outer circumference of said elongate bar (14) when received at said base plate (12).

3. The system as claimed in claim 1 wherein, said second sliding rail (16b) is positioned, offset with respect to said elongate bar (14), such that said corresponding sensor (17b) is tangential, establishing point contact, to an outer circumference of said elongate bar (14) when received at said base plate (12).

4. The system as claimed in claim 1 wherein, said third sliding rail (16a) is positioned, offset with respect to said elongate bar (14), such that said corresponding sensor (17c) is tangential, establishing point contact, to an outer circumference of said elongate bar (14) when received at said base plate (12).

5. The system as claimed in claim 1 wherein, said fourth sliding rail (16d) is positioned, offset with respect to said elongate bar (14), such that said corresponding sensor (17d) is tangential, establishing point contact, to an outer circumference of said elongate bar (14) when received at said base plate (12).

6. The system as claimed in claim 1 wherein, said elongate bar is a hollow (14a) elongate bar with weights that can be added in the hollow segment (14a) of said metallic bar.

7. The system as claimed in claim 1 wherein, said elongate bar elongate bar (14) comprising:
- a base plate (14b) which allows it to couple to said robot (10);
- a first elongate element (14a) protruding operatively vertically, downwards from an underside of said base plate (14b); and
- a stub element (14c), coaxial to said first elongate element (14a), protruding, operatively vertically, further downwards from a farther end of said first elongate element (14a); said stub element (14c) configured to interface with said system’s base plate (12) when said robot (10) moves towards said; thereby, establishing contact with relevant sensors to sense angular displacement, linear displacement, and / or effect of weight and / or velocity of said robot (10).

8. The system as claimed in claim 1 wherein, said elongate bar (14) being configured to:
- Swivel, angularly, about its pivot point where it interfaces with said base plate (12); and
- Move, axially, operatively upwards and operatively downwards, through its pivot point where it interfaces with said base plate (12).

9. The system as claimed in claim 1 wherein, each of said sensors (17a, 17b, 17c, 17d) are on a locus of points equidistant from a centre, said centre being defined as a point where said first elongate arm (14) rests on said base plate (12).

10. The system as claimed in claim 1 wherein, said first sensor (17a) and the third sensor (17c) are collinearly aligned.

11. The system as claimed in claim 1 wherein, said second sensor (17b) and the fourth sensor (17d) are collinearly aligned.

12. The system as claimed in claim 1 wherein, each sensor is angularly displaced by an adjacent sensor by an angle of 90 degrees.

13. The system as claimed in claim 1 wherein, each of said sensors (17a, 17b, 17c, 17d) is linked on to said corresponding sliding elements (16a, 16b, 16c, 16d) with resilient mechanisms such that said resilient mechanism’s naturally resting position leads to said sensor touching said elongate rod (14) and upon action of forces, its resilient forces compress, displace said sensor, leading to sensing and recording values of said sensor, and leading said sensor back to its naturally interfacing tangential position.

Dated this 22nd day of March, 2022

CHIRAG TANNA
of INK IDÉE
APPLICANT’S PATENT AGENT
REGN. NO. IN/PA – 1785