Critical Thinking

Modelling, 112 Osama Saeed 14 – ME –

Modelling, Repairing and Upgradation
of Test Bench for      Recoil Mechanism


Ahsan Naseer                                    14 – ME – 109

Israr Ahmed                                      14 – ME –

M. Osama
Saeed                             14 – ME
– 142

A Final year project submitted in
partial fulfillment of the requirements for the degree of

B.Sc. Mechanical Engineering

Project Advisor:

Dr. Riffat Asim Pasha

Professor and Chairman MED



Examiner Signature:_____________________________________________

Project Advisor Signature:_____________________________________________




January 2018



Bench for Recoil Mechanism

            The recoil mechanism is an independent hydro pneumatic system.
hydraulic Recoil Mechanism is a way of limiting the effects of recoil and
adding to the accuracy and firepower of an artillery piece. The project deals
with the modelling of test bench for recoil mechanism for the purpose of
repairing and upgrading it. Through modelling the fault in apparatus can be
easily identified and system can be modified. The apparatus contain
electrohydraulic valves, Hydraulic cylinder, pump and an electric motor which
are highly nonlinear devices. Bond graph is a convenient tool for modelling
nonlinear elements. The state space equations are derived using the natural
laws of science and by using bond graph approach. These nonlinear equations
will then be simulated in some appropriate equation solver software. Simulation
will also be done in 20-Sim software. The response of system will be predicted
in terms of graphs and modification will be carried out.


Recoil mechanism test bench

Test bed for recoil

Modeling and Control of Hydraulic Actuator



WE certify that
final year project titled “Modelling,
Repairing and Upgradation of Test Bench for Recoil Mechanism” is our own
work. The work has not been presented elsewhere for assessment. Where material
has been used from other sources it has been properly acknowledged / referred.





Ahsan Naseer                                                                                
   Israr Ahmed

14 – ME – 109                                                                                   14
– ME – 112



Osama Saeed

14 – ME – 142




of all we are thankful to Allah who gives us the wisdom and resources for this
work. After than we are thankful to Ex- General Manager, Descom Heavy
Industries Taxila Brig. Dr. Muhamad Adnan Qasim for introducing and leading us
to the way of modelling. We are thankful to our Project advisor Dr. Riffat Asim
Pasha for helping us and equipping us with the books for our knowledge.
Appreciation also goes to HIT management for letting us work in their facility
and financially supporting our work.


Abstract 2
Undertaking. 3
Acknowledgement 4
Table of Figures. 6
Abbreviations. 7
1.      Introduction. 8
1.1.       Problem Statement 8
1.2.       Objectives. 9
2.      Description of Internal Mechanism.. 9
3.      Modelling. 11
3.1.       The Bond Graph (BG) Approach. 11
3.2.       Modelling Description. 12
3.2.1.        Electric Motor 12
3.2.2.        Pump. 13
3.2.3.        Hydraulic Cylinder 15
3.2.4.        Electro-hydraulic Valve (EHV) 16
3.2.5.        Miscellaneous. 18
3.3.       Overall Bond Graph Representation. 18
3.4.       Result in terms of Graph. 19
4.      Project Progress. 19
References. 20



Table of Figures


Figure 1- Recoil Mechanism Cylinders 8

Figure 2- Schematic of Hydraulic System_ 9

Figure 3- A permanent Magnetic AC Motor 12

Figure 4- DC series Motor and corresponding BG_ 13

Figure 5- A Displacement Pump (Schematic) 13

Figure 6- Bond Graph Model of Pump_ 14

Figure 7- Hydraulic Cylinder 15

Figure 8- BG representation of Hydraulic Cylinder 16

Figure 9- Internal Passages in an EHV_ 17

Figure 10- Bond Graph Behavior 17

Figure 11 Bond Graph Representation of entire Model 18

Figure 12- Graph b/w Pressure, Velocity and Position
vs Time_ 19



Final Year Project                  FYP

Undergraduate                                    UG

Bond Graph                            BG

Electro-Hydraulic Valve        EHV

Pressure Regulator Valve      PRV

Speed Regulator Valve          SRV

Gyrator                                   GY

Transformer                            TF

Inertia                                     I

Compliance                             C

Resistance                               R

Modulated Resistance                        MR

Modulated Transformer         MTF

Modulated Gyrator                 MGY

One Junction                           1

Zero Junction                          0

Chapter # 01



means the backward motion of the of the gun when we discharge the weapon this
phenomenon is also referred as kickback in technical terms it practically
applies the newton’s third law of motion whereas the mechanism carrying out the
phenomenon is called recoil mechanism which is basically the core of our study.
The hydraulic recoil mechanism which is used in the artillery in the tanks is
of immense important being responsible for giving accuracy to the weapon and
reducing the effects created by recoil mechanism thus nullifying any possible
chance of breakage, wreckage of the apparatus. This hydraulic recoil mechanism
is tested over the recoil test bench which we eventually tend to repair and

Figure 1- Recoil Mechanism

hydraulic recoil mechanism test bench comprises of hydraulic, mechanical and
electrical systems in order to provide with the similar exerted pressure which
we face in the actual recoil mechanism. To know the basic problem we first have
to consider the structure of the recoil test bench, at the back end it has two cylinders
one filled with the oil and the other filled with oil and air partially, the
later one comprising of both the oil and the air provides with the reaction and
acts as a spring. The purpose of the accommodation of spring-like adjustment is
to avoid any possible chances of breakage in the tank gun.

normal circumstances the test bench works in appropriate manner and help us
provide familiar conditions to the gun barrel in order to test it but the
certain hydraulic test bench under consideration is out of order thus we first
were required to identify the problem causing the seizure of the test bench and
sorting out the problem in order to repair the test bench, further we tend to
upgrade the hydraulic test bench with innovation reducing any chances of
further seizures. As mentioned earlier the test bench comprised of both
electrical and mechanical systems thus by processing different parts of the
test bench separately we identified the spot creating the problem. The details
of the operations carried out to identify the problem, solution and upgradation
will be further discussed in later stages.


objective of this Report is to present work done on entitled project. First The
test bench will be modelled and state space equations will be derived. Based on
those state space equations the response of the system at any desired time or
given input can be predicted.  These
equations can be simulated in proper software like 20-sim and graphs are shown
at the end of this report. The system will also be practically checked and
repaired. We proposed to add data acquisition system in the equipment as its
upgradation. It will allow checking the behavior of recoil mechanism better
than before and storing the information.


Figure 2- Schematic of
Hydraulic System

Description of Internal Mechanism

The hydraulic system
consists of following parts:

·       Oil filter:
Oil filter WC37-50
is a net filter which is mounted on the oil suction pipe to defend the oil

·       Vane type oil pump: Vane type oil pump
YB-50 is used for conversion of the mechanical energy transmitted to the motor
into the hydraulic energy which is used as the hydraulic driving force.

·       Over-flow valve:
pressure over flow valve Y1-63B is used as safety valve on the machine which
limits the pressure in the hydraulic system to a certain value and protects the
hydraulic system from over load. The pressure regulating limits are 3-63

·       Cock of the pressure gauge:
Cock of the pressure gauge K-1B is a small stop valve which is used for the
cut-in and cut-off the oil way.

·       Speed regulating valve:
Speed regulating valve Q-63B
is used for adjusting the speed of the cylinder motion. The adjusting limits of
flow rate are 0.06-63 Liter/minute.

·       Electro-hydraulic valve:
Electro-hydraulic valve 34DY-6382
 plays the role of guiding. The flow reversing
is controlled with the aid of electromagnetic valve. Speed is adjusted by
one-way throttle valve, located in the control oil way and on the hydraulic
valve pod.

·       Hydraulic Cylinders:
Hydraulic Cylinders of type RS06-002 are used to convert the pressure into
force in order to check the recoil mechanism cylinders.



Part No







Oil Cylinder for pulling test






Oil Filter






Vane type oil pump


Q=501/min H=63kg/cm^2






N=7.5kw , n=970 r.p.m




Over-flow valve
(medium pressure)






Cock of the pressure guage






Speed Regulating Valve






Electro-hydraulic valve






Oil cylinder for screwing in packing
box nut






Pressure guage






Chapter # 02


The Bond Graph
(BG) Approach

of the whole equipment was done through bond graph technique. Bond
graph, short for the power bond graph, is a graphical approach to deal with
multiple energy categories of engineering system, based on the law of
conservation of energy. The bond graph method was proposed by Professor
H.M.Paynter of MIT in 1959 and developed into a modeling theory and method by
Karnopp and Rosenberg1. Now bond graph method has been widely used
for teaching, research and engineering development in universities and
engineering in such countries as the United States, the Netherlands, France,
Britain, Germany, Canada, India, Japan, Australia, etc.

modelling is a powerful tool for modelling engineering systems, especially when
different physical domains (e.g. Mechanical, Electrical and Hydraulics) are
involved. Furthermore, bond-graph sub models can be re-used elegantly, because
bond-graph models are non-causal. The sub models can be seen as objects;
bond-graph modelling is a form of object-oriented physical systems modelling.

bond graph generalizes a variety of physical parameters into four kinds of
state variables, namely effort, flow, momentum and displacement, which can
represent any physical components in the actual system. Bond consists of the
power bond and the signal bond, of which power bond is commonly used. The power
bond is a line segment, with a half arrow and a short vertical line, is used to
connect bond-graph components. The half arrow indicates the direction of energy
flow and positive power transport, and the short vertical line represents the
causality. The main effect of the causality is to determine the relationship
between two bond-graph components, i.e., one is the reason for the power
transmission, and the other is the result of the power transmission. In bond
graph, the e (effort) and f (flow) pair are carried by a single power bond, and
their product is equal to the power transmitted by this power bond.

are nine components in bond graph, they are effort source (Se), flow source
(Sf), resistive element (R), capacitive element (C), inertial element (I),
transformer (TF), gyrator (GY), “0” junction and “1”
junction. We can draw the corresponding block diagram as long as the direction
of the power flow and causality between these components are determined.





3.2.1.     Electric

Commonly an
electric motor is represented by a gyrator “GY” in bond graph. Here gyrator
converts Electric current into Torque and Voltages into rotational Speed such
that the total power of the system remains conserved.

Figure 3- A permanent Magnet AC Motor

Figure 3- A permanent
Magnetic AC Motor









            The poles shown in above figures creates magnetic field
which is responsible for establishing a relationship between the electrical
domain, which is an input side in E. Motor and the Mechanical Domain which it
output (i.e. rotation). In case of permanent magnet this field remains constant
but in case of separately excited motor such as Shunt or series motor the field
is the function of current through which we established magnetic field.
Therefore output aslo becomes function of the input field current. In the give
case a DC series motor is used, separately excited by field current “if”
and input current “ia” and input voltage “ea” and ‘ef’
is field voltage 3.

The equation corresponding to
figure-2 is given.



And ‘

‘ and ‘

‘ are torque and rotational speed and ‘

‘ is transduction coefficient.

Figure 4- DC series Motor and
corresponding BG

figure 4 the ‘I’ before and above ‘MGY’ represents Self Induction,  ‘R’ is Resistance and ‘I’ after ‘MGY’ is
polar moment of inertia and ‘R’ is rotating friction loss.


pump that is presented for modelling is displacement pump since it is simpler
to model than centrifugal or any other rotary pump. There
are many analogies between rotary electromechanical devices and hydro
mechanical devices. Just as a dc motor with multiple windings and a commutator
functions as a gyrator, a pump with several pistons and a porting arrangement
functions essentially as a transformer. The field port of a dc motor allows
modulation of the gyrator parameter, and a stroke control on a pump, if it
exists, allows modulation of the transformer ratio.

Figure 5- A Displacement Pump

it is clear from the figure-5 first the rotary motion that is because of the
rotation of motor is to be transformed into reciprocating motion of Piston
which is than further to be transformed into hydraulic pressure. The force upon
the Piston can be easily transformed into pressure that is it is easy to move
from the reciprocating domain to hydraulic domain. The relations are given.

            Here ‘A’ that is area of piston is acting as transformer ratio. ‘F’ is
force of piston, ‘P’ is pressure, ‘V’ is piston velocity and ‘Q’ is hydraulic
flow rate. Therefore it can be easily represent by a transformer in bond graph.

take a look at the first step that is to convert the rotary motion into
reciprocating motion. It is rather difficult to understand. It can be represented
by a modulated Transformer in BG model. Here the transformer ratio will be a
function of angle ”







For simplification purposes, the
equation can be represented in the following form.




Figure 6- Bond Graph Model of



3.2.3.     Hydraulic

Figure 7- Hydraulic Cylinder

Cylinder is device to convert hydraulic pressure of pump into force that is
needed to move the piston of recoil mechanism that is to be attached with the
test bench. It contains ram whose operation and bond graph model is similar to
that was discussed earlier in pump’s second part in which we converted force
into pressure. Of course here will be the reverse phenomena. Therefore
transformer ‘Tf’ function will be usen in bond graph model. Here in this model,
some non-linearity will also be added into our model. These are as given.

1)     Internal
and External Leakage.

2)     Friction.

3)     Hydraulic
Oil Compressibility.

4)     Piston
Area difference (since A1 = A2). This creates force

Some of these nonlinearities were also present in
Pump. That is friction and internal leakage. Compressibility that is added here
will account whole model.

Oil compressibility is given as.


V0 = Volume of the section.

B  = Bulk
modulus of oil.

internal and external leakage, the following relationship will be used.


Figure 8- BG representation of
Hydraulic Cylinder

And ‘µ’ is oil viscosity, ‘L’ will be length along leakage, ‘di’
is the diameter of piston and ‘rc’ is the radial clearance between
piston and cylinder walls.2

            The above
relation that accounts for leakage can also be used in pump.

            To account for
friction the resistance ‘R’ above force ‘F’ bond is used. Here the basic
relation will be same as the basic relation for resistor as described above but
here the value of ‘R’ will be changed.


            Here ‘FF’
will be frictional force ‘Vp’ is the velocity of piston and ‘Kv’
is the viscous force coefficient. Also here ‘R = Kv’.

            The same
relation will be used to evaluate force of friction in Pump.

3.2.4.     Electro-hydraulic
Valve (EHV)

valve is used to set the direction of cylinder piston. Therefore it acts as a
controller in equipment. It has a spool valve as shown in figure that sometimes
prevent the hydraulic fluid to cross sometimes it allows it to flow it from one
direction and other thereby controlling the whole process. This spool is
actuated by solenoid valves, which are placed at its both ends that provide
displacement ‘z’ that controls the flow of oil. There are internal passages in
EHV as shown in figure-9.

Figure 9- Internal Passages in
an EHV

EHV provides four
passages for oil to flow. Its function is similar to Wheatstone bridge. Its
bond graph model will be shown in the end with the whole model.

Figure 10- Bond Graph Behavior

Here flow when non-linear behavior is added.


            Here ‘Q’ is flow rate, ‘P’ is pressure, ‘Cd’
coefficient of discharge and ‘A(z)’ is the area to which flow has to pass. Here
it can be seen that area ‘A(z)’ depends upon the spool displacement ‘z’.

above relation is also used for Speed regulator valve (SRV) and Pressure
Regulator Valve (PRV).

3.2.5.     Miscellaneous

are some other relations that are used in model. Such as the resistance to
hydraulic oil flow is given1. But the condition to use this
relation is that Reynold number should be less than 2000.

And the hydraulic Inertia is also considered in calculations.

            In above
relations ‘

‘ is density of oil, ‘L’ is the overall
length to which fluid has to approach, ‘

‘ is fluid viscosity and ‘d’ and ‘A’ are
pipe diameter and cross-section.

Overall Bond
Graph Representation

Figure 11 Bond Graph
Representation of entire Model


Figure 12- Graph b/w
Pressure, Velocity and Position vs Time

Result in terms of Graph

above bond graph representation was simulated and above graph was generated
automatically only after giving values to all variables and constants. Some of
the values were known and some are assumed.

4.    Project

Results were shown after putting some values. Some of the values to dimensional
variables that we didn’t know are assumed for right now. A general trend has
been shown. This will remain the same but its magnitude can vary after putting
accurate values to dimensional variables. Moreover Control of the system
remains to be added. State space equations also needed to be derived. The
system is now in working condition and upgradation is in progress.





Dean C. Karnopp, Rosenberg, System Dynamics Modelling and Simmulation of
Mechatronics System, 5th edition.

B. Sulc, J. A. Jan, Nonlinear modelling and Control of Hydraulic Actuators,
Vol. 42, No. 3/2002

Nayana P. Mahajan, Dr. S.B. Deshpande, Study of the nonlinear behavior of DC
Motor using Modelling and Simmulation, International Journal of Scientific and
Research Publications, Volume 3, Issue 3, March 2013

Jun Yan, Bo Li, Hai-Feng Ling, Hai-Song Chen, and Mei-Jun Zhang, Nonlinear
State Space Modeling and System Identification for Electrohydraulic Control,
Hindawi Publishing Corporation, Mathematical Problems in Engineering ,Volume
2013, Article ID 973903, 9 pages