arXiv subjects

Chris Waltham

Publications and source records attributed to Chris Waltham.

8 recordsLinked to original sources

arXiv2026

OpenPodcar2: a robust, ROS2 vehicle for self-driving research

OpenPodcar2 is a robust, ROS2-interfaced, low-cost, open source hardware and software, autonomous vehicle platform based on an off-the-shelf, hard-canopy, mobility scooter donor vehicle. It is a modification of the previous OpenPodcar design, which extends it with robust electronics and ROS2 interfacing, to enable both research and also potential deployment use cases. The platform consists of (a) hardware components: documented as a bill of materials and build instructions; (b) integration to the general purpose OSH R4 mechatronics board and a Gazebo simulation of the vehicle, both presenting a common ROS2 interface (c) higher-level ROS2 software implementations and configurations of standard robot autonomous planning and control, including the nav2 stack which performs SLAM and enacts commands to drive the vehicle from a current to a desired pose around obstacles. OpenPodcar2 can transport a human passenger or similar load at speeds up to 15km/h, for example for use as a last-mile autonomous taxi service or to transport delivery containers similarly around a city center. It is small and safe enough to be parked in a standard research lab robust enough for some deployment cases. Total build cost was around 7,000USD from new components, or 2,000USD with a used Donor Vehicle. OpenPodcar2 thus provides a research balance between real world utility, safety, cost and robustness.

cs.RO↗

arXiv2024

R4: rapid reproducible robotics research open hardware control system

A key component of any robot is the interface between robotics middleware software and physical motors. New robots often use arbitrary, messy mixtures of closed and open motor drivers and error-prone physical mountings, wiring, and connectors to interface them. There is a need for a standardizing OSH component to abstract this complexity, as Arduino did for interfacing to smaller components. We present a OSH printed circuit board to solve this problem once and for all. On the high-level side, it interfaces to Arduino Giga - acting as an unusually large and robust shield - and thus to existing open source software stacks. A ROS2 interface is provided. On the lower-level side, it interfaces to existing emerging standard open hardware including OSH motor drivers and relays, which can already be used to drive fully open hardware wheeled and arm robots. This enables the creation of a family of standardized, fully open hardware, fully reproducible, research platforms.

cs.RO↗

arXiv2023

OpenPodcar: an Open Source Vehicle for Self-Driving Car Research

OpenPodcar is a low-cost, open source hardware and software, autonomous vehicle research platform based on an off-the-shelf, hard-canopy, mobility scooter donor vehicle. Hardware and software build instructions are provided to convert the donor vehicle into a low-cost and fully autonomous platform. The open platform consists of (a) hardware components: CAD designs, bill of materials, and build instructions; (b) Arduino, ROS and Gazebo control and simulation software files which provide standard ROS interfaces and simulation of the vehicle; and (c) higher-level ROS software implementations and configurations of standard robot autonomous planning and control, including the move_base interface with Timed-Elastic-Band planner which enacts commands to drive the vehicle from a current to a desired pose around obstacles. The vehicle is large enough to transport a human passenger or similar load at speeds up to 15km/h, for example for use as a last-mile autonomous taxi service or to transport delivery containers similarly around a city center. It is small and safe enough to be parked in a standard research lab and be used for realistic human-vehicle interaction studies. System build cost from new components is around USD7,000 in total in 2022. OpenPodcar thus provides a good balance between real world utility, safety, cost and research convenience.

cs.RO↗

arXiv2011

An Early History of Heavy Water

Since 1945 Canada has had a nuclear power industry based on reactor design which uses natural uranium and heavy water. The tortuous and improbable sequence of events which led to this situation is examined.

physics.hist-ph↗

arXiv2011

A versatile sensor for string motion

The full characterization of a stringed musical instrument requires measuring the motion of the strings in at least two dimensions. Traditionally this has been done using electromagnetic means or by optical transmission. However in many instruments the strings are not made of steel, nor are the strings easily accessible on both sides. In this work it is shown that string positions can be measured by inexpensive optical reflection sensors which neither require metallic strings nor obtrusive access. We have demonstrated a versatile and non-invasive technique for measuring the position of a vibrating string in a 1 mm^2 area with an accuracy of tens of microns for thin strings, and better than 0.1 mm for thick ones.

physics.ins-det↗

arXiv2003

Neutrino Oscillations for Dummies

The reality of neutrino oscillations has not really sunk in yet. The phenomenon presents us with purely quantum mechanical effects over macroscopic time and distance scales (milliseconds and 1000s of km). In order to help with the pedagogical difficulties this poses, I attempt here to present the physics in words and pictures rather than math. No disrespect is implied by the title; I am merely borrowing a term used by a popular series of self-help books.

physics.ed-ph↗

arXiv2002

"Bernoulli" Levitation

"Bernoulli" levitation is the basis of many popular counter-intuitive physics demonstrations. However, few of these lend themselves to a quantitative description without recourse to computational fluid dynamics. Levitation of a flat plate is the exception, and we present here a straightforward analysis which illustrates several principles of fluid mechanics in a pedagogically useful way.

physics.ed-ph↗

arXiv2002

A Three-Dimensional Calculation of Atmospheric Neutrino Fluxes

We present a three-dimensional calculation of atmospheric neutrino fluxes using accurate models of the geomagnetic field, hadronic interactions, tracking and decays. Results are presented for the Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) sites using the GEANT-FLUKA hadronic code. We make a comparison with previous one-dimensional calculations and other three-dimensional results. The recently reported geometrical enhancement of low energy, horizontal neutrinos is confirmed. The effect on observed leptons is however, restricted to a small overall increase in flux. We report east-west asymmetries for each of the neutrino species.

hep-ph↗