12 research outputs found
On the synthesis of driver inputs for the simulation of closed-loop handling manoeuvres
This paper concerns a new ‘Dual Model’ methodology for the synthesis of steering, throttle and braking
inputs for the closed-loop simulation of linear or non-linear vehicle handling dynamics. The method
provides near-optimal driver control inputs that are both insensitive to driver model assumptions, and
feasible for use with complex non-linear vehicle handling models. The paper describes the Dual Model
technique, and evaluates its effectiveness, in the context of a low-order non-linear handling model, via
comparison with independently derived optimal control inputs. A test case of an obstacle avoidance
manoeuvre is considered. The methodology is particularly applicable to the design and development of future chassis control systems
Simultaneous optimisation of vehicle parameter and control action to examine the validity of handling control assumptions
In this paper a general method is presented for optimising system parameters and inputs. The
Generalised Optimal Control technique involves iterative resimulation of system states, but is
applicable to any (smoothly) nonlinear system, and can be operated using non-quadratic cost functions.
Here it is applied to find optimal steer and torque inputs for a 2DOF vehicle handling model with a
(combined slip) nonlinear tyre model. System parameters for centre of gravity and yaw inertia are
simultaneously optimised, and hence the validity of some handling control assumptions – particularly
the benefits of zero sideslip – is examined. The results are satisfactory, and they are mainly in keeping
with expectation. The method is proven to be effective, though computationally rather expensive
Comparison of optimal driving policies for limit handling manoeuvres
This paper concerns the synthesis of optimal control inputs for automotive handling dynamics, a typical
application being in the evaluation of active safety systems operating near the limits of friction. The
paper considers an example of an emergency limit handling manoeuvre – combined acceleration and
steering to achieve obstacle avoidance whilst also maximising speed and maintaining stability. Two
independent methods are applied to the problem. The first is a general numerical optimiser for nonlinear
control systems (Generalised Optimal Control, or GOC). The second is an indirect Dual Model
(DM) method, which has the advantage that no differential analysis of the vehicle model is required,
and it can therefore be applied directly to a wide range of complex multibody dynamic models. A
relatively low-order handling model is actually used within this study, since this allows comparison
between the two methods and an evaluation of the general usefulness of the DM approach in the future
A randomized integral error criterion for parametric identification of dynamic models of mechanical systems
This paper proposes a new approach to the identification of reduced order models for
complex mechanical vibration systems. Parametric identification is commonly conducted by the
regression of time-series data, but when this includes significant unmodelled modes, the error process
has a high variance and autocorrelation. In such cases, optimization using least-squares methods can
lead to excessive parameter bias. The proposed method takes advantage of the inherent boundedness
of mechanical vibrations to design a new regression set with dramatically reduced error variance.
The principle is first demonstrated using a simple two-mass simulation model, and from this a
practicable approach is derived. Extensive investigation of the new randomized integral error
criterion method is then conducted using the example of identification of a quarter-car suspension
system. Simulation results are contrasted with those from comparable direct least-squares identifications.
Several forms of the identification equations and error sources are used, and in all cases
the new method has clear advantages, both in accuracy and consistency of the resulting identification
model
Combined state and parameter estimation of vehicle handling dynamics
This paper considers an extended form of the wellknown
Kalman filter observer, to reconstruct dynamic
states from a small sensor set, but also to rapidly adapt
selected parameters in the nonlinear dynamic model
which lies at the heart of the observer. A generic
procedure is described for constructing the extended
Kalman filter in such a way that any combination of
model parameters can be identified.
The study is carried out in simulation, using two
different vehicle dynamic models, one to act as the test
vehicle, the other forming the nucleus of the observer.
The assumption is that while in-vehicle testing is most
desirable for proving many controller algorithms, here we
need ‘true’ reference state information, to examine
Kalman filter accuracy.
A number of experiments are carried out to prove the
system’s identification properties and also to compare its
performance with a more conventional Kalman filter,
based on a linear handling model. The results
demonstrate high levels of performance and significant
robustness to design parameters such as parameter
adaptation speed and anticipated sensor noise. Most
significantly, the observer also operates well and is
capable of parameter adaptation when model and sensor
covariance information is not available – usually a
restricting factor in practical Kalman filter estimator
design. The only significant caveat is that we are
‘buying’ excellent dynamic tracking from a small sensor
set, at some computational expense
An application of multimedia in teaching mechanical vibrations
An application of multimedia in teaching mechanical vibration
Development of a Master of Science programme in Automotive Systems Engineering
Development of a Master of Science programme in Automotive Systems Engineerin
Influence of anti-dive and anti-squat geometry in combined vehicle bounce and pitch dynamics
The paper presents a six-degree-of-freedom (6-DOF) multi-body vehicle model, including realistic representation of suspension kinematics. The suspension system comprises anti-squat and anti-dive element. The vehicle model is employed to study the effect of these features upon combined bounce and pitch plane dynamics of the vehicle, when subjected to bump riding events. The investigations are concerned with a real vehicle and the numerical predictions show reasonable agreement with measurements obtained on an instrumented vehicle under the same manoeurves
A comparison of braking and differential control of road vehicle yaw-sideslip dynamics
Two actuation mechanisms are considered for the comparison of performance capabilities
in improving the yaw–sideslip handling characteristics of a road vehicle. Yaw moments are generated
either by the use of single-wheel braking or via driveline torque distribution using an overdriven active
rear differential. For consistency, a fixed reference vehicle system is used, and the two controllers are
synthesized via a single design methodology. Performance measures relate to both open-loop and
closed-loop driving demands, and include both on-centre and limit handling manoeuvres
An agent-based traffic simulation framework to model intelligent virtual driver behaviour
This paper presents an agent-based traffic simulation framework that supports intelligent virtual driver behaviour. The framework exploits concepts used in Artificial Life (ALife), Artificial Intelligence (AI) and Agent technology to model the inherent unpredictability and autonomous behaviour of drivers within traffic simulation models. Each driver agent in our system contains knowledge and a decision-making mechanism, both of which are based on heuristics. This approach replaces some of the prescriptive nature of driving simulation models by allowing behaviours to emerge as a result of individual driver agent interactions. The framework also contributes to accident analysis by improving current limitations in which accident investigation methods concentrate on the events themselves, rather than pre-crash influences. Within this context, the framework provides an opportunity to increase the understanding of accident causation factors, to examine alternative traffic scenarios (what if analyses) and methodology to obtain quantitative estimates of accident risk. Current implementation results show that driver agents within the integrated simulation are able to perceive other drivers’ speeds and distances, avoid collisions, perform realistic vehicle following, and demonstrate emergent traffic flow. A major application area for this framework includes the evaluation of vehicle, highway and road user factors that precede a collision, or near misses