Longitudinal Dynamic versus Kinematic Models for Car-Following Control Using Deep Reinforcement Learning

The majority of current studies on autonomous vehicle control via deep reinforcement learning (DRL) utilize point-mass kinematic models, neglecting vehicle dynamics which includes acceleration delay and acceleration command dynamics. The acceleration delay, which results from sensing and actuation delays, results in delayed execution of the control inputs. The acceleration command dynamics dictates that the actual vehicle acceleration does not rise up to the desired command acceleration instantaneously due to dynamics. In this work, we investigate the feasibility of applying DRL controllers trained using vehicle kinematic models to more realistic driving control with vehicle dynamics. We consider a particular longitudinal car-following control, i.e., Adaptive Cruise Control (ACC), problem solved via DRL using a point-mass kinematic model. When such a controller is applied to car following with vehicle dynamics, we observe significantly degraded car-following performance. Therefore, we redesign the DRL framework to accommodate the acceleration delay and acceleration command dynamics by adding the delayed control inputs and the actual vehicle acceleration to the reinforcement learning environment state, respectively. The training results show that the redesigned DRL controller results in near-optimal control performance of car following with vehicle dynamics considered when compared with dynamic programming solutions.Comment: Accepted to 2019 IEEE Intelligent Transportation Systems Conferenc

Some aspects of local immunity and pathogenesis in rodents infected with Nippostrongylus brasiliensis or Trichostrongylus colubriformis

Summary available: p. i-v

A novel micromechanical model of nonlinear compression hysteresis in compliant interfaces of multibody systems

The final publication is available at Springer via http://dx.doi.org/10.1007/s11044-015-9483-6A micromechanical model of nonlinear hysteretic compression between interacting bodies of multibody systems, covered with fibrous structures, has been created and validated experimentally in this work. As an application, a multibody dynamic model of an upright piano action mechanism with felt-covered contacting bodies is considered, and the obtained results were verified using experiments. Felt, as a typical nonwoven fiber assembly, has been used in various contact surfaces of piano action mechanisms to transfer the force applied on the key to other components, smoothly and continuously. To keep the simulation time tractable in the mechanistic multibody dynamic model, interaction between felt-lined interfaces has to be simplified enough so that in each step of simulation time, contact forces can be calculated as a function of penetration depth between colliding objects. The developed micromechanical approach is capable of estimating nonlinear bulk response of felt in terms of microstructural parameters of the network, assuming a binomial distribution of the number of fiber contacts and bending of constituent fibers. Hysteresis is included based on a fiber-to-fiber friction approach, which generates a speed-independent response to compressive loading schemes, as has been observed in experiments. A computational algorithm is introduced to apply the sophisticated hysteretic micromechanical model to the multibody systems simulation, including transitions between loading–unloading stages.The authors gratefully acknowledge the Financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC)

A study of volumetric contact modelling approaches in rigid tyre simulation for planetary rover application

© Inderscience Enterprises Ltd. The original source of publication is available at InderScience. Petersen, W., & McPhee, J. (2014). A study of volumetric contact modelling approaches in rigid tyre simulation for planetary rover application. International Journal of Vehicle Design, 64(2–4), 262–279. https://doi.org/10.1504/IJVD.2014.058489For planetary rover applications, a volumetric contact modelling approach is used to capture the dynamics of the rigid tyre/soil interface. The volumetric contact model allows for determining closed-form expressions for the tyre contact forces. These volumetric force representations contain information about the shape of the contact geometry so that the analytical expressions result in fast simulations. Three different volumetric rigid tyre models are developed and evaluated from a plasticity point of view. The performance of each tyre is tested and compared with respect to the resistance force caused by the ongoing compaction of the soil and the resultant plastic deformation. The quantity used to model the plastic deformation of the soil is represented by the soil rebound. Moreover, each tyre model is compared against experimental data to evaluate its validity

Foot–ground contact modeling within human gait simulations: from Kelvin–Voigt to hyper-volumetric models

The final publication is available at Springer via http://dx.doi.org/10.1007/s11044-015-9467-6This study describes the development of a multibody foot–ground contact model consisting of spherical volumetric models for the surfaces of the foot. The developed model is two-dimensional and consists of two segments, the hind-foot, mid-foot, and fore-foot as one rigid body and the phalanges collectively as the second rigid body. The model has four degrees of freedom: ankle x and y, foot orientation, and metatarsal-phalangeal joint angle. Three different types of contact elements are targeted: Kelvin–Voigt, linear volumetric, and hyper-volumetric. The models are kinematically driven at the ankle and the metatarsal joints, and simulated horizontal and vertical ground reaction forces as well as center of pressure location are compared against experimental quantities acquired from barefoot measurements during a human gait cycle. Parameter identification is performed for finding optimal contact parameters and locations of the contact elements. The hyper-volumetric foot–ground contact model was found to be a suitable choice for foot/ground interaction modeling within human gait simulations; this model showed 75 % and 62 % improvement on the matching quality over the point contact and linear volumetric models, respectively.Natural Sciences and Engineering Research Council of Canada (NSERC

Automated topology optimisation of hybrid electric vehicle powertrains

Ing, A. H., & McPhee, J. (2015). Automated topology optimisation of hybrid electric vehicle powertrains. International Journal of Electric and Hybrid Vehicles, 7(4), 342. Final version published by Inderscience Publishers, and available at: https://doi.org/10.1504/IJEHV.2015.074671Gasoline and electric powertrain components can be connected in numerous configurations to create hybrid powertrains. Owing to the exponential increase of permutations as the number of components increases, a framework to determine the best possible powertrain configuration that minimises fuel consumption was developed. This framework uses enumeration to discover all powertrains, the Graph-Theoretic Method to generate system equations, dynamic programming to evaluate fuel consumption and generate an objective score, and Pattern Search to optimise the sizing of each component. A multi-stage screening process was used to reduce computation time. Parallel and powersplit-like topologies with additional discrete gearboxes were found to be the most efficient. The best performing topology is a powersplit hybrid type: a discrete gearbox connected to the final drive, with the output gear of the planetary carrier and electric motor in parallel.The project is funded by Toyota, Maplesoft, and NSERC