SPACE ROBOTICS BY MOSES DHILIP KUMAR

SPACE ROBOTICS

 BY MOSES DHILIP KUMAR

INTRODUCTION

              

Robot is a system with a mechanical body, using computer as its brain. Integrating the sensors and actuators built into the mechanical body, the motions are realised with the computer software to execute the desired task. Robots are more flexible in terms of ability to perform new tasks or to carry out complex sequence of motion than other categories of automated manufacturing equipment. Today there is lot of interest in this field and a separate branch of technology ‘robotics’ has emerged. It is concerned with all problems of robot design, development and applications. The technology to substitute or subsidise the manned activities in space is called space robotics. Various applications of space robots are the inspection of a defective satellite, its repair, or the construction of a space station and supply goods to this station and its retrieval etc.   With the over lap of knowledge of kinematics, dynamics and control and progress in fundamental technologies it is about to become possible to design and develop the advanced robotics systems. And this will throw open the doors to explore and experience the universe and bring countless changes for the better in the ways we live.

ABSTRACT

               Robot is a mechanical body with the brain of a computer. Integrating the sensors and the actuators and with the help of the computers, we can use it to perform the desired tasks. Robot can do hazardous jobs and can reach places where it’s difficult for human beings to reach. Robots, which substitute the manned activities in space, are known as space robots. The interest in this field led to the development of new branch of technology called space robotics. Through this paper, I intend to discuss about the applications, environmental condition, testing and structure of space robots.

SPACE ROBOT—CHALLENGES IN DESIGN AND TESTING

               Robots developed for space applications will be significantly different from their counter part in ground. Space robots have to satisfy unique requirements to operate in zero ‘g’ conditions (lack of gravity), in vacuum and in high thermal gradients, and far away from earth. The phenomenon of zero gravity effects physical action and mechanism performance. The vacuum and thermal conditions of space influence material and sensor performance. The principle effect of distance is the time delay in command communication and its repercussions on the action of the arms. The details are discussed below

SYSTEM VERIFICATION AND TESTING

                   The reliability is to be demonstrated by a number of tests enveloping all the environmental conditions (thermal and vacuum) that the system will be subjected to. Verification of functions and tests will be conducted on subsystems, subassemblies and final qualification and acceptance tests will be done on complete system. The most difficult and the nearly impossible simulation during testing will be zero ‘g’ simulation.

1       Flat floor test facility: It simulates zero ‘g’ environments in the horizontal plane. In this system flat floor concept is based on air bearing sliding over a large slab of polished granite.

2       Water immersion: Reduced gravity is simulated by totally submerging the robot under water and testing. This system provides multi degree of freedom for testing. This method is used by astronauts for extra vehicular activities with robot.

3       Compensation system: Gravitational force is compensated by a passive and vertical counter system and actively controlled horizontal system.. However, the counter mechanism increases the inertia and the friction of joints of rotating mechanism.

ROBOT CALIBRATION

Calibration is performed in five steps:

·       Identification, which uses the parametric model and the measured data to determine the optimal set of error parameters.

·       Model implementation, which may be done either by updating the root controller data or by correcting the robot pose with expected standard deviation of the error.

·       Verification, that the improvement in the positioning accuracy of the robot in all three axes have been achieved.

STRUCTURE OF SPACE ROBOTS

SPACE SHUTTLE ROBOT ARM (SHUTTLE REMOTE MANIPULATOR SYSTEM)

1. USE OF SHUTTLE ROBOT ARM

               Satellite deployment and retrieval

·       Construction of International Space Station

·       Transport an EVA crew member at the end of the arm and provide a scaffold to him or her. (An EVA crew member moves inside the cargo bay in co-operation with the support crew inside the Shuttle.)

·       Survey the outside of the Space Shuttle with a TV camera attached to the elbow or the wrist of the robot arm.

Shuttle robot arm observed from the deck

2 ROBOT ARM OPERATION MODE

                   SRMS is operated inside the Space Shuttle cabin. The operation is performed from the aft flight deck (AFD), right behind the cockpit; either through the window or by watching two TV monitors. To control the SRMS, the operator uses the translational hand controller (THC) with his or her left hand and manipulates the rotational hand controller (RHC) with his or her right hand.

                                     THC                                        RHC    

3. FREE FLYING SPACE ROBOTS

                   The figure below shows an example of a free flying space robot. It is called ETS VII (engineering test satellite VII). It was designed by NASDA and launched in November 1997. When the robot arm moves, it disturbs the altitude of the satellite base. This is not desirable because,

·                         The satellite may start rotating in an uncontrollable way.

·                         The antenna communication link may be interrupted.

Free flying space robots

4. SPACE STATION MOUNTED ROBOTS

                   The international space station (ISS) is a sophisticated structural assembly. There will be several robot arms which will help astronauts in performing a variety of tasks.

JEMRMS

                   The figure shows a part of ISS including the Japanese Experimental Module (JEM). A long manipulator arm can be seen. The arm is called JEMRMS (JEM Remote Manipulating System). A small manipulator arm called SPDM (Special purpose dexterous Manipulator) can be attached to JEMRMS to improve the accuracy of operation.

                                             SPDM

5. SPACE ROBOT TELEOPERATION

                   Space robotics is one of the important technologies in space developments. Especially, it is highly desired to develop a completely autonomous robot, which can work without any aid of the astronauts. However, with the present state of technologies, it is not possible to develop a complete autonomous space robot. For this reason, it has become highly desired to develop the technologies for the teleoperation of space robots from the ground in the future space missions.

CONCLUSION

               In the future, robotics will make it possible for billions of people to have lives of leisure instead of the current preoccupation with material needs. There are hundreds of millions who are now fascinated by space but do not have the means to explore it. For them space robotics will throw open the door to explore and experience the universe.

REFERENCES

1.       www.andrew.cmu.edu/~ycia/robot.html

2.       www.space.mech.tohoku.ac.jp/research/overview/overview.html

3.       www.nanier.hq.nasa.gov/telerobotics-page/technologies/0524.html

 

RAPID PROTOTYPING BY MOSES DHILIP KUMAR

RAPID PROTOTYPING

This document provides a detailed description and a brief understanding about the rapid prototyping.

THEME: Enhancing the detailed importance and need of RAPID PROTOTYPING in the society.

Introduction

Rapid prototype is an excellent output from the thirst of millions of scientist , the main promotion of the model lies in its skill where it reduces the time for experimenting an model without much cost and effort.

DEFENITION

ORIGIN

Rapid prototyping is the automatic construction of physical objects using additive manufacturing technology. The first techniques for rapid prototyping became available in the late 1980s and were used to produce models and prototype parts. Today, they are used for a much wider range of applications and are even used to manufacture production-quality parts in relatively small numbers.

WORKING

With additive manufacturing, the machine reads in data from a CAD drawing and lays down successive layers of liquid, powder, or sheet material, and in this way builds up the model from a series of cross sections. These layers, which correspond to the virtual cross section from the CAD model, are joined together or fused automatically to create the final shape. The primary advantage to additive fabrication is its ability to create almost any shape or geometric feature.

The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Smaller facets produce a higher quality surface.

INTERFACING

The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Smaller facets produce a higher quality surface.

SIGNIFICANCE

Rapid Prototyping has also been referred to as solid free-form manufacturing, computer automated manufacturing, and layered manufacturing. RP has obvious use as a vehicle for visualization. In addition, RP models can be used for testing, such as when an airfoil shape is put into a wind tunnel. RP models can be used to create male models for tooling, such as silicone rubber molds and investment casts. In some cases, the RP part can be the final part, but typically the RP material is not strong or accurate enough. When the RP material is suitable, highly convoluted shapes (including parts nested within parts) can be produced because of the nature of RP.

HELPFUL AREAS

Used in in-house utilities

Used in comparative analysis

Used in comprehensive testing

TECHNOLOGICAL INNOVATIONS THAT OVERTOOK THE DIFFICULTIES AFTER THE INVENTION OF RAPID PROTOTYPE BEFORE                    AT PRESENT
An complete model is done for experimental and for a testing purpose	Just an prototype is desingned so that it can be tested and can be used for the consultation of betterment
An extensive time period is spent in the dept of testing	A lot of time and power has been saved
Cost of production is increased which reduces its popularity.	Cost of production is much reduced.
In case of difficulty in the existing model it cannot be replaced immediately with out complete comprehensive test .	In case of any difficulty it can be easily verified and also can be rectified using the designed prototype.
If the tested model is failure due to some design model it is not that easy to create such an another model	But in the prototype it is much easier .

Good prototype model

OLD METHOD OF TESTING

Modern ways of testing

PROTOTYPE’S SIGNIFICANCE:

Increasingly companies are attaching greater importance to the need to differentiate their product and service offerings in order to remain competitive. Typically, firms are:

adding new technologies to our products to differentiate;

forming alliances with our   customers;

adding service features to our manufactured product offerings;

reducing time to market for new products;

reducing the number of suppliers and forming longer-term relationships and alliances with those that remain;

expanding the product range; and reducing their cost base to become the lowest cost producer.

MAIN DISADVANTAGES OF RAPID PROTOTYPE :

When dealing rapid prototyping technologies, seven major strategic issues need to be explored

The strategic nature of the technologies - aspects of rapid prototyping which take investment decisions beyond the realm of short-term return on investment calculations;

The technologies as enablers of new strategies - the new business and marketing strategies that can be pursued as a result of using these technologies;

The impact of rapid prototyping on the achievement of business objectives - the specific business objectives that can be directly affected by applying the technologies;

Strategic aspects of organisational and cultural changes - what organisational and culture changes does the business strategy itself demand;

Development of change competencies - applying rapid prototyping technologies to achieve operational change competency, and developing tactical and strategic change competencies to enable continuing developments in rapid prototyping to be deployed to satisfy existing business objectives and to develop new strategies;

Development and exploitation of knowledge - using existing knowledge and developing new knowledge for competitive advantage.

WHY WE NEED IT:

The sale of this product with others because it is much easier to see if there are problems with the design and organization of a real working model

It is also much easier to sell to potential customers when they have a rapid prototyping to hold and manipulate a presentation marketing.

 Without a prototype is just an idea.

 It can be difficult to get a client to participate in a purchase of one concept.

With prototype in hand, the concept becomes real and the moment is much easier .

We  should keep in mind during the prototype phase as well. Regardless of how developers and testers that a prototype can be, consumers may not real, as some of its aspects.

 If the end customer does not like, they will not buy, which explains why the focus groups and external tests with the prototypes to be addressed before production begins.

 Patent If a product is new or unique bit excessive, patents must be considered.

It is useless to design and produce a great product to another company only begins to produce a product very similar, because the original company patented key design elements.

Having a working prototype is much easier to sit with a lawyer to see what aspect of the design may be patentable.

 On the back, you can see parts of the prototype and the design of infringing patents of others and how they can be changed before production, and the possibility of a trial begins.

BASIC LEVEL OF A COMPLETE PROTOTYPING MODEL AND A FLOW CHART SCENARIO.

 

INCONVINIENCE IN USING RAPID PROTOTYPING MACHINE:

Needs co operation of workers to finish an complete model successfully.

Higer officials may consider prototyping as an wasteful needed process

Programmer may loose discipline

The prototype may influence the design

The pror=totype model may be overworked.

LUXURY OF PROTOTYPE

Unattended operation

This system is fully automated that is doesn‘t require any attention

during the operation.

Good accuracy

The SLA able to produce a very high accuracy

˜

0.001“

High detailing

SLA is capable of producing an intricate design with high precision.

Surface finish

The —printed part“ has a very smooth surface.

Industry presence

SLA was the first RP to be introduced into the market. It constituted

1% of the worldwide market based on sales.

The part may melt if exposed to high temperature for a period of time.

 

 Influence of design by rapid prototype

The prototype may have an influence on your design which should be taken care of.

A GOOD MODEL

AN AVERAGE MODEL

STEPS TO REDUCE THE ABOVE MENTIONED INCONVINIENCE:

The material chose should be apt and easily adoptable.

The material chosen should always be in an position to be cooled fast by the cooler used.

The complication of the prototype should be reduced in the stl files used.

CONCLUSION:

Henceforth being well aware of this engineering excellence of a rapid prototype ,  being an engineer we should be well enough acquired to readily accept the advancement in such area which would greatly enhance our career.

ABSTRACT

This paper is based on the project “Power Assisted Gear Shifting Mechanism for Automobiles”. This is a design, fabrication and implementation project. The project provides solution for gear shifting for the cars. The passenger cars that now ply on the road have transmission either of manual or automatic type of gear changing. The manual type of transmission is preferred for the perfect performance without a loss in power but a compromise for comfort ness. In this type automatic system of power transmission there is easiness of gear shifting but there is a definite loss of power and mileage. The main objective of this project is to create a mechanism to reduce the inconvenience caused when changing gears in the car. The gear shifting here is by mere pressing of feather touch buttons present on the dash board. The gear shifting is by hydraulic force achieved by a simple modification to the gear box. This is a versatile pack, simple and can be fitted to any car equipped with hydraulic power steering. The setup consists of power steering pump, piston cylinder assembly and a set of fluid valves. This project if implemented is a clear alternative for the Automatic transmission because of its low cost and ease of use. Moreover the whole set up is small and requires a very small space. This can sure be a standard fitment if proper marketing strategy is carried out. Further, automatic clutch can be incorporated with this unit to make it fully automatic.

                          PROJECT MODEL

INTRODUCTION

            The paper deals with the real time project, “Power Assisted Gear Shifting Mechanism for Automobiles” which was done in the academic year 2004- 2005. The paper deals with the various design aspects of the creation of this project. This project is aimed at giving driver the convenience for gear shifting. The car with this project will have a series of buttons in the format of 4 forward, a reverse and a neutral. The clutch operation may or may not be put in the car depending on the user. Currently the project has been done for the transmission of third and reverse gears.  The power for gear shifting is got from hydraulic fluid. The power for fluid is from the power steering pump. So a car with a power steering fitment can be easily adaptable to this project. The project has been started as a concept and it requires a lot more work to be done to put in a car.

PROBLEM DEFINITION

            Whenever a project is carried out there is a reason behind it. The existing cars now pose some problems for the drivers. In the Manual Transmission cars the main problem for the drivers is the gear shifting. But the engineering concept behind this type of transmission paves way for higher power transmission efficiency. More over the mileage of the car and life is also more. These cars do not give much of comfort ness for the drivers in the terms of using the gear lever and the clutch. Also it occupies a major area in the cabin resulting in the space congestion. These are the problems in the Manual Transmission cars.

         

          In the Automatic Transmission type of cars, the gear shifting is easy. We just have to select the drive band, which is already preset. This selection may be either of lever type or a set of buttons. This is easy for the drivers as they don’t have to use clutch during gear shift. But there is a compromise for power transmission and mileage. As the gear selection is by a fluid, power is required to drive it, so the engine performance is reduced.  So the problem here is mileage drop, power loss and also it is costly.

          The need of the hour, combining the position of both MT and AT a mechanism has to be created for better mileage and comfortable gear shifting. This is the objective of the project. So a car with this project provides ease of gear shift as in AT without a compromise in mileage as in MT. the cost of the project is less as it requires a minor alteration in the gear box.

DESIGN OF PROJECT

            The project is done as a table top on the FIAT car’s gear box. The project design comprises of designing the following parts,

1.     Hydraulic circuit

2.     Electronic circuit

3.     Mechanical components

HYDRAULIC CIRCUIT

            Hydraulic motion is selected for gear shifting owing to its large load acceptance and ease of adaptability in the car. Also the gear shift should be quick. The basic components design is explained in detail.

CYLINDER DESIGN

Load required to move the selector rod or to change the gear F=30 Kg

Pressure built in the compressor unit                                      P=10 bar

To find:

Cylinder dimensions D,L=?

1. Cylinder diameter D=?

          P=F/A

    (10*10⁵)*(P/4)*D² = 30*9.81

D=0.0194 m = 20 mm

2. Cylinder length L =?

     Cylinder length L= Stroke Length+ Piston thickness+ Clearance

       L= 30+10+7 = 47 mm

                          L=47mm

Cylinder diameter= 20mm                          Cylinder length= 47mm

SELECTION OF PUMP

Selection of pump is based on following characteristics:

1. Select the actuator that is appropriate based on loads encountered.

2. Determine the flow rate requirements. This involves the calculation of the flow rate               necessary to drive the actuator to move the load through a specified distance within the given time.

3. Determine the pump speed and select the prime mover. This, together with the flow rate calculation, determines the pump size

4. Select the pump based on application

5. Select the system pressure. These involves in with the actuator size and magnitude of the resistive force produced by the external load on the system. Also involved here is the total amount of power to be delivered by the pump.

6. Select the reservoir and associated plumping, including piping, valving, hydraulic cylinders, motors and other miscellaneous components.

7. Calculate the overall cost of the system.

8. Consider factors such as noise levels, horse power loss, need for a heat exchanger due to heat generated, pump wear, scheduled maintenance service to provide a desired life of the total system.

The above characteristics are satisfied by the GEAR OIL PUMP and the following data are obtained from measurement,

Do =75 mm Di =50 mm W= 25 mm N=1440 rpm

1. Flow rate Q= (P/4)*(Do²-Di²)*W*N

                   = (P/4)*(0.075²-0.050²)*0.050*1440

                   = 0.0883 m³/S = 0.00147 m³/min = 1.47 Ltrs/min

2. Power required = Pressure*Flow rate= (10*10⁵)*0.0883 = 88.3 kw

SELECTION OF RESERVIOR

1. Reservoir Capacity= 2.5 to 3 Times of Pump flow

= 3*1.47

= 4.41 Ltrs

=4 Ltrs

2. Size of the copper tube =6 mm(for transmitting hydraulic fluid to valves

HydraulicCircuitDiagram

Hydraulic circuit diagram of the project

1. Reservoir.                                     7. Cylinder piston assembly

2. Pump.                                  8.  Limit Switch

3. Clutch                                  9. Gear Box

4. Engine                                 10. Gear selector rod

5. Inlet Solenoid Valve            11. Spring

6. Outlet Solenoid Valve        

ELECTRONIC CIRCUIT

The electronic circuit is used for governing the hydraulic operation. For this purpose we have used two solenoid valves (inlet and outlet) for each gear to be shifted. The supply voltage is from battery which is 12V. there will be six buttons 1, 2, 3, 4, R, N for gear shifting. Each actuates the gear corresponding when pressed.

The diagram below shows the electronic circuit for various operation of the gear shifter.

i. Engaging first gear

ii. Maintaining gear position

iii. Releasing gear-neutral position

iv. Gear changing

                

MECHANICAL COMPONENTS

The main mechanical component for the project is the spring. The spring is used to counter balance the force exerted by the piston. Moreover it is useful in the return motion of the gear selector rod during gear disengagement. Presence of spring on the gear selector rod helps in the quick action that is required during the gear shift.

DESIGN OF SPRINGS

We have formula for deflection         Y = 8PD³n/Gd⁴

Where,

Y=deflection of spring

P=load acting on the spring

D=Diameter of spring

d= Diameter of spring coil

N=no of coils in the spring

G=modulus of elasticity of spring material

G=2*10⁵ N/mm²

D=3.5 Cm

d=0.4 Cm

P=30 Kg

Y=1.5 Cm

No of coils in the spring,

          n=YGd⁴/8PD³

= 1.5*2*10⁵*0.4⁴*100/(8*30*9.81*3.5³)

= 8 coils

WORKING PRINCIPLE

              The main driving force for the gear shifting is by the hydraulic fluid. The gear shifting along with the clutch operation works with the pressing of buttons. On pressing the button corresponding to the gear, three operations take place,

1.     Engine rotation

2.     Clutch engagement

3.     Pump rotation

                  

             When the car is switched on the engine rotates, on pressing the button clutch engages. Now electromagnetic clutch engages the pump. Due to the pump rotation the hydraulic fluid is pumped from reservoir to the inlet solenoid valve. Through this valve the fluid pushes the piston in the cylinder. This motion causes the gear shifter rod to engage the gear which is fitted to the piston. In order to avoid slippage of gear a limit switch is used to sense the position of selector rod and cut off the supply.

                To bring the car to neutral position we press the N button. Now the outlet solenoid valve energizes so the fluid in the cylinder rushes back to the sump with the aid of spring tension. If the next higher gear has to be selected, the same operation takes place on pressing the next button.

                    

CURRENT STATUS

Presently we have done this project as a table top working model. This consists of various parts which are listed below.

1)    FIAT Gearbox

2)    TOYOTA Power steering compressor

3)    Motor for driving the compressor

4)    Electro magnetic clutch

5)    Tank or reservoir for storing the hydraulic fluid

6)    Valves for controlling the flow of hydraulic fluid

7)    Limit switch to cut off the supply

8)    Hydraulic cylinder and piston assembly

9)    Copper tubes for transportation of fluid

10)                       Fluid Hoses

11)                       Base structure for holding the gearbox and motor arrangement

The current model is a simple one which is actuated by a stick switch governing the gear selection. This set up works good for two gears. In the future there are plans to incorporate the clutch action in the set up by using the electronic clutch.

MERITS AND DEMERITS

          A project with a novel idea does have its own merits and demerits which are discussed below,

Merits:

¨     A clear alternative for Auto Transmission this, is much cheaper and user friendly with more features.

¨     Leg room for passengers at front is increased more since the removal of gear rod.

¨     Ease of operation, by the use of feather touch buttons.

¨     A boon for the handicapped, the car can be driven even with only one hand since buttons are used for changing gears.

¨     No loss in mileage of the car as the load required for gear shift is meager.

¨     Gear shift is sequential, so no problem of wrong gear selection.

Demerits:

Since the project is custom made, it requires a skilled technician to assemble the set up in the car, considering the space constraints. Moreover the driver should be well trained in using the system to avoid malfunction.

CONCLUSION

This project is an innovative concept. It is a new dimension in the transmission system of a car. This is a simple and versatile pack that may be fitted to any cars existing with power steering. By implementing this smart gear shifter in cars, we can achieve more space, smooth operation, more user friendly, less effort to change the gear and no play. Also the project is a boon for physically challenged persons. The present condition of the project is promising for further developments. Lots of inputs are also got from the car specialists and academicians for its improvement. The concept can be transformed to a real time fitment on further development. We estimate a period of two years to see a car fitted with this mechanism.

REFERENCE