Course work assignment

EEE6203/EEE6210

Course work assignment

Jiabin Wang

5/12/2014

1. Introduction

As a part of the assessment for EEE6203 and EEE6210, the students are required to complete the course work outlined in the follow sections. The course work is concerned with modelling, control design and simulation of a permanent magnet (PM) machine drive system, and its applications in electric vehicle (EV) tractions or aerospace actuations. It will contribute 25% of the overall assessment.

The course work is structured in two parts. The first part, which is common for both EEE and Aerospace students, is to build a simulation model of the PM machine drive system and perform appropriate

simulation studies and performance evaluation. The second part is application specific case studies. For EEE students, the work is to build and simulate an EV traction system based on the drive model

established in part one while aerospace students will construct a representative flight surface control actuation system with the drive model in part one. Subsequent simulations and evaluations are to be performed.

2. Specifications

2.1. Permanent magnet motor

Machine topology Number of pole-pairs Connection Continuous/pear power (kW) Phase resistance at 120 oC (mΩ) Synchronous inductance (mH) Flux linkage per phase (mWb) Torque constant (Nm/A peak) Back-emf constant (V peak s/rad) Base speed (rpm) Maximum speed (rpm) Continuous current (A peak/rms) Maximum current (A peak/rms, > 2 minutes) Moment of inertia (kg m2)

2.2. Transmission and vehicle data for EV traction system Fig. 1 shows the schematic of a distributed EV power train configuration in which the traction power is provided by two motors coupled to the front and rear axles via differentials. This power train is intrinsically fail-safe since any failure in one drive will not result in a complete loss of power.

You only need to simulate one drive system, assuming the other is identical and the traction torque is shared equally between the two. The vehicle and transmission data are given below:

Surface mounted permanent magnet 7 Star 5.0/10.0 22.2 0.344 39.6 0.415 0.277 1350 5500 85/60.5 170/121 0.008

Fig. 1 Schematic of distributed EV power

trains

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Fig. 2 Micro-sized EV for urban mobility

Vehicle data:

• Tyre size: 165/50 R15

• Radius of wheels rw = 0.273; • Vehicle mass m = 800;

• Gravitational acceleration g = 9.80665; • Rolling resistance coefficient kr = 0.007;

• Product of drag coefficient and front area CdA = 0.35; • Air density rho = 1.25;

• Differential gear ratio Gr = 4

• Efficiency of differential Et = 0.98; • Drive cycle: NEDC, data to be provided • DC-link voltage 120V

2.3. Transmission and mechanical layout for flight control surface actuation All aircraft include movable control surfaces for directional control in flight, Fig. 3.

(a) Control surfaces

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(b) Control system block diagram Fig.3 Aircraft control surfaces

Such control surfaces can include primary flight control surfaces for general flight path control, as well as various lift and drag devices for take-off and landing. Primary flight control surfaces can include ailerons for roll control, elevators for pitch control, and rudders for yaw control. Conventional lift and drag devices can include leading edge slats, trailing edge flaps, and spoilers. A typical spoiler and hinge for a control surface driven by a linear electromechanical actuator is shown in Fig. 4.

SpoilerHome positionRHingexLθFig. 4 Mechanical spoiler and hinge

θ

Fig. 5 Electromechanical actuator and actuation system

layout

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The actuator is driven by the permanent magnet brushless motor whose parameters are given in section 2.1 via an integrated ball screw and planetary gear transmission. The pitch of the ball screw is 10mm, the gear ratio of the planetary gear is 0.2, and the transmission efficiency is 0.88. The moment of inertia of the spoiler is 24.07kgm2.

The geometric distance, R, of the actuator arm to the hinge at the home position is 0.2m, and L = 0.65m. The torque acting on the hinge due to aerodynamic drag as a function of the angular displacement θ is given by:

Torque on hinge (Nm) θ (degree)

-15 5531 20 -1475 30 -13275 40 -25075 and illustrated in Fig. 6.

100005000Hinge torque (Nm) 0-5000-10000-15000-20000-25000-30000Angular deflection (Deg) -15-10-50510152025303540

3. Simulation environment and prerequisite

The maximum load torque for emergency descent is 22,000 Nm. The DC bus voltage for actuator is 270V

Fig. 6 Variation of hinge torque with angular deflection

The course work will be aided by simulation studies in Matlab/Simulink environment and the students will need basic knowledge and skill in modelling and simulation with Matlab/Simulink. If your ability to use the simulation tool is relatively weak, please read relevant materials [1-2] and books, and do your own practice with some examples. It should be noted that to ensure all students use the same platform for the course work, SimPowerSystems or Simscape are not allowed to use.

4. Tasks

4.1. Common tasks for both EEE and aerospace students (60%)

In this task, a simulation model with torque control of the PM machine drive based on specification given in section 2.1 should be established. It is advised that the following steps are taken to perform this task

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(a) PM machine model in dq reference system

(b) PM machine model in ABC reference system with the model built in (a) as well as ABC to dq

and dq to ABC transformations

(c) Design dq axis PI current controller with a bandwidth of 800Hz

(d) Build dq axis current controller with over modulation protection and anti-winding up (e) Integrate current controller into the machine model in ABC reference system (f) Perform simulation and evaluation under torque control model

(g) An inverter model with space vector modulation is integrated into the drive system model

and operation demonstrated. This subtask is optional, but additional 10 marks will be awarded if it is completed

4.2 Separate tasks for EEE and aerospace students (40%) EEE students: (a) Extend the PM machine drive model under torque control to include transmission, vehicle

mass, drag and rolling resistance

(b) Design speed control loop for vehicle cruise control with a bandwidth of 80Hz and build

complete system model

(c) Perform simulation of EV traction system over New European Driving Cycle (NEDC) (d) Evaluation and discussion Aerospace students (a) Extend the PM machine drive model under torque control to include the transmission, and

mechanical spoiler and hinge

(b) Design speed and position feedback loops and build complete system model

(c) Perform simulation studies with representative turbulence and bird-strike as disturbances (d) Evaluation and discussion

5. Report and assessment

A short report of no more than 20 pages should be submitted for assessment together with the simulation model you have constructed and simulated. Marks will be awarded against the quality of report and achievements.

References

[1] http://www.mathworks.co.uk/academia/student_center/tutorials/launchpad.html

[2] http://www.mathworks.co.uk/academia/student_center/tutorials/simulink-launchpad.html

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