Longitudinal Vehicle Dynamics Part 2

Question 1

1) Definition of braking ratio:
a. Braking ratio between ideal and real;
b. Ratio between braking torque and braking force;
c. Ratio between ideal braking torque and ideal braking force.

Answer 1

b. Ratio between braking torque and braking force;

Question 2

2) The ideal braking curve depends:
a. On the mass;
b. On the center of gravity position;
c. Both.

Answer 2

c. Both.

Question 3

3) The ideal braking curve is:
a. A straight line;
b. A parabola;
c. A logarithmic curve.

Answer 3

b. A parabola;

Question 4

4) To calculate the deceleration in braking in four wheels (equilibrium wheel ground) it must be considered:
a. Total vehicle mass;
b. Apparent translating mass;
c. An intermediate value between them.

Answer 4

a. Total vehicle mass;

Question 5

5) For the dimensioning of the braking system of a heavy vehicle which of the following conditions is usually most critical?
a. The downhill driving;
b. The mixed route of a mountain;
c. Frequent acceleration and deceleration.

Answer 5

a. The downhill driving;

Question 6

6) Which condition is worse for a light vehicle in braking?
a. In downhill;
b. In mixed route in braking;
c. Frequent acceleration and deceleration.

Answer 6

c. Frequent acceleration and deceleration.

Question 7

7) When the braking torques are such to block all the wheels, the braking is:
a. In ideal conditions;
b. In real conditions, depending on the type of the system;
c. If the proportioning valve is adequately designed, in ideal conditions.

Answer 7

a. In ideal conditions;

Question 8

8) If μxf=μxr the braking is:
a. Always in ideal conditions;
b. In real conditions;
c. In ideal conditions with the proportioning valve.

Answer 8

a. Always in ideal conditions;

Question 9

9) If in braking μ xf >μxr :
a. The vehicle is oversteering ;
b. There is no influence over the handling if both μ x are lower than the maximum adherence; c. The vehicle is understeering.

Answer 9

The vehicle is understeering.

Question 10

10) { ́z}=[ A] .{z}+[ B] .{u} how are called the matrices [A] and [B]?
a. [A] dynamic matrix, [B] input gain matrix;
b. [A] dynamic matrix, [B] output gain matrix;
c. [A] input gain matrix, [B] dynamic matrix.

Answer 10

a. [A] dynamic matrix, [B] input gain matrix;

Question 11

11) At locked control, the variables are:
a. β, r and δ;
b. β, r and δ = const.;
c. β, r and δ = input.

Answer 11

c. β, r and δ = input.

Question 12

12) In order to make kinematic steering possible:
a. The normal at the medium planes of the steering wheels must converge;
b. The normal at the medium planes of all the wheels must converge to a point;
c. The normal at the medium planes of all the wheels must converge to a point over the y axis.

Answer 12

b. The normal at the medium planes of all the wheels must converge to a point;

Question 13

13) Which influence has (C Mz)β over the stability of the vehicle and its critical speed? a. If it’s > 0 the critical speed decreases, making the vehicle instable; if its < 0 do not appear any critical speed, and the vehicle is stable;
b. If it’s < 0 the critical speed decreases, making the vehicle instable; if its > 0 do not appear any critical speed, and the vehicle is stable;
c. If it’s = 0 do not appear any critical speed, and the vehicle is stable.

Answer 13

b. If it’s < 0 the critical speed decreases, making the vehicle instable; if its > 0 do not appear any critical speed, and the vehicle is stable;

Question 14

14) By what is it more influenced the directional behavior?
a. By the adherence;
b. By the rigidity of the driving axle;
c. By the rigidity of the driven axle.

Answer 14

a. By the adherence;

Question 15

15) Definition of neutral vehicle:
a. l=Rδ ,1l=1Rδ
b. R=lδ, 1R=1lδ
c.l=Rδ , δ=Rl

Answer 15

a. l=Rδ ,1l=1Rδ

Question 16

16) The sideslip angles of a neutral vehicle:
a. Are equal to the kinematic ones;
b. Are equal for rear and front axles;
c. Are different for rear and front axles.

Answer 16

b. Are equal for rear and front axles;

Question 17

17) Equal sideslip angles for two axle vehicles determine incompatibility with the linearization? a. Yes;
b. No;
c. No, only for kinematic steering in which α1=α2=0.

Answer 17

c. No, only for kinematic steering in which α1=α2=0.

Question 18

18) The linearized models for the study of the directional behavior are valid for driving conditions in which (n.b. for small angles it’s understood angles in which the trigonometric functions are linearized):
a. All the angles are small;
b. The angles are in general not small;
c. The angles are small, but the sideslip angles are such that they do not prevent the linearization of the drifting forces.

Answer 18

a. All the angles are small;

Question 19

19) The semi-linearized models allow:
a. Only the numeric integration of the equations of motion;
b. The study of the stability in general;
c. To obtaining general solutions for the response to the command of the steering.

Answer 19

a. Only the numeric integration of the equations of motion;

Question 20

20) The limit case of the kinematic steering is valid as:
a. The smaller is the speed;
b. The bigger is the curve radius;
c. For neutral vehicles.

Answer 20

a. The smaller is the speed;

Question 21

21) The kinematic steering radius of a semitrailer with non-steering axle:
a. Is greater than the steering radius of the truck;
b. Is equal to the steering radius of the truck;
c. Is smaller than the steering radius of the truck.

Answer 21

c. Is smaller than the steering radius of the truck.

Question 22

22) The load transfer over wheels on a same axle:
a. Doesn’t influence the directional behavior;
b. Always influence the directional behavior;
c. Influences it only if it overcomes a certain value.

Answer 22

c. Influences it only if it overcomes a certain value.

Question 23

23) In an articulated with semitrailer with one axle, the hypothesis that the wheels have the same sideslip angle:
a. Derives from the linearization of the model;
b. Derives from the linearization of the characteristics of the tire;
c. Derives from the linearization of the trigonometric functions of the angle. ϑ

Answer 23

a. Derives from the linearization of the model;

Question 24

24) In a 3 dof model for the study of the directional behavior of the isolated vehicle, at the equation of
motion in longitudinal coordinates, the decoupling can be made if:
a. Inertial coordinates;
b. Coordinates axle-body;
c. Y is at the center of the trajectory.

Answer 24

b. Coordinates axle-body;

Question 25

25) In a system mass spring damper:
a. Q>2√PU behaves in non-oscillatory motion ( understeer );
b. Q<2√PU behaves in dampened oscillatory motion ( oversteer );
c. Q=2√ PU is neutral.

Answer 25

c. Q=2√ PU is neutral.

Question 26

26) In a vehicle with 3 dof the lateral acceleration cannot be high because:
a. Otherwise the load transfer is too high over a single axis (there is an increase of the cornering stiffness of the overloaded wheel that is not compensated by the reduction on the less loaded one);

Answer 26

a. Otherwise the load transfer is too high over a single axis (there is an increase of the cornering stiffness of the overloaded wheel that is not compensated by the reduction on the less loaded one);

Question 27

27) In a first approximation of a motorbike, the gyroscopic momentum has an importance: a. Negligible;
b. Great importance;
c. Not great, but neither negligible.

Answer 27

c. Not great, but neither negligible.

Question 28

28)L/Rδ for a vehicle that steers in kinematic conditions is an expression:
a. Exact;
b. Approximated, but the more exact as the more the vehicle kinematics reaches the kinematic
condition;
c. Approximated …

Answer 28

c. Approximated …

Question 29

29) The transversal adherence of a vehicle calculated from the sliding factor, with respect to the one of the tire, is:
a. Greater;
b. Equal;
c. Smaller.

Answer 29

c. Smaller.

Question 30

30) The adoption of an antiroll bar influences:
a. In whichever conditions;
b. Only in conditions of strong lateral forces;
c. At low adherence conditions.

Answer 30

b. Only in conditions of strong lateral forces;

Question 31

31) The effect of the traction over the directional behavior is as more sensible as: a. The greater is the cornering stiffness of the driving axle;
b. The lesser is the adherence;
c. The lesser is the cornering stiffness of the driving axle.

Answer 31

b. The lesser is the adherence;

Question 32

32) The expression Y =Y β. β+Y r.r+Y δ. δ is valid:
a. Always;
b. At the hypothesis of linearization of the angles;
c. At the hypothesis of total linearization of the model.

Answer 32

c. At the hypothesis of total linearization of the model.

Question 33

33) The condition of stability is:
a. Real part positive;
b. Real part negative;
c. Imaginary part negative.

Answer 33

b. Real part negative;

Question 34

34) The presence of a steering axle on the trailer on an articulated truck (discordant steering) introduces a kind of recall force that tends to align the vehicle. The effect of such force:
a. Is the one of increasing the dynamic stability;
b. Over the dynamic stability is null;
c. Is the one of decreasing the dynamic stability.

Answer 34

c. Is the one of decreasing the dynamic stability.

Question 35

35) The relationship that connects the steering angle with the radius of the curve of the trajectory 1
l=1Rδ in kinematic conditions is valid if:
a. R is big with respect to l;
b. l is big with respect to R ;
c. It is always valid.

Answer 35

a. R is big with respect to l;

Question 36

36) The steady-state response of a vehicle under a lateral wind gust depends:
a. On the distance from the medium point of the center of gravity;
b. On the distance from the point of application of the aerodynamic force to the center of gravity; c. On the distance from the point of application of the aerodynamic force to the neutral point.

Answer 36

c. On the distance from the point of application of the aerodynamic force to the neutral point.

Question 37

37) The steering of the rear axles of the trucks is:
a. In general concordant;
b. In general discordant;
c. Depends on the velocity.

Answer 37

c. Depends on the velocity.

Question 38

38) The critical speed is present:
a. On all types of vehicles;
b. Only on oversteering vehicles;
c. Only on understeering vehicles.

Answer 38

b. Only on oversteering vehicles;

Question 39

39) The study of the directional behavior of a vehicle with more than two axles can be executed using the 2 dof model studied for 2 axle vehicles:
a. True;
b. True, if calculated the load Z acting over the various axles considering the suspensions; c. False.

Answer 39

b. True, if calculated the load Z acting over the various axles considering the suspensions;

Question 40

40) In the case of an understeering vehicle, the application of a lateral force at the center of gravity:
a. Curves the trajectory towards the direction of the force;
b. Curves the trajectory towards the opposite direction of the force;
c. Does not curve the trajectory.

Answer 40

b. Curves the trajectory towards the opposite direction of the force;

Question 41

41) In a rigid body model with 3 dof , the equation relative to the degree 1 of freedom x, is separated
from the others if:
a. It is linearized and solved apart;
b. Are neglected the interactions between the forces Y and X of the tires;
c. …….

Answer 41

b. Are neglected the interactions between the forces Y and X of the tires;

Question 42

42) At the study of the motion at free control, the input is usually:
a. The steering angle δ;
b. The torque exerted on the steering wheel M G ;
c. The self-alignment torque of the wheels.

Answer 42

b. The torque exerted on the steering wheel M G ;

Question 43

43) In order to study the directional behavior of a vehicle as a rigid vehicle it is necessary to build a mathematical model with:
a. 10 dof ;
b. 4 dof , reducible to 3;
c. 3dof , reducible to 2.

Answer 43

c. 3dof , reducible to 2.

Question 44

44) When is it possible the overturning?
a. When fr> fs;
b. Never;
c. Depends on the road conditions.

Answer 44

c. Depends on the road conditions.

Question 45

45) The steering radius of a trailer with non-steering axles:
a. Is greater than R (steering of the truck);
b. Is equal to R (closed circuit and reload);
c. Is smaller than R (steering of the truck).

Answer 45

c. Is smaller than R (steering of the truck).

Question 46

46) The steering radius of a trailer with steering axle:
a. Is greater than R (steering of the truck);
b. Is equal to R (closed circuit and reload);
c. Is smaller than R (steering of the truck).

Answer 46

a. Is greater than R (steering of the truck);

Question 47

47) There is stability when the eigenvalues of the equation { Z}={Zo } est have:
a. Negative real part;
b. Positive real part;
c. Negative imaginary part.

Answer 47

a. Negative real part;

Question 48

48) There is stability when the eigenvalues of the equation { Z}={Zo} eiλ have:
a. Negative real part;
b. Positive real part;
c. Positive imaginary part.

Answer 48

c. Positive imaginary part.

Question 49

49) Usually it is given the hypothesis that the sideslip angles α f=αr. This hypothesis:
a. Is rigorous given that the steering mechanism respect the kinematic steering conditions; b. Is coherent with the linearization of the model;
c. Is valid only if the suspensions are neglected.

Answer 49

b. Is coherent with the linearization of the model;

Question 50

50) A model with 3 dof for a truck has how many equations?
a. 3;
b. 4;
c. 6.

Answer 50

b. 4;