arXiv subjects

Matthew Woodward

Publications and source records attributed to Matthew Woodward.

4 recordsLinked to original sources

arXiv2025

Real-Time Trajectory Generation and Hybrid Lyapunov-Based Control for Hopping Robots

The advent of rotor-based hopping robots has created very capable hopping platforms with high agility and efficiency, and similar controllability, as compared to their purely flying quadrotor counterparts. Advances in robot performance have increased the hopping height to greater than 4 meters and opened up the possibility for more complex aerial trajectories (i.e., behaviors). However, currently hopping robots do not directly control their aerial trajectory or transition to flight, eliminating the efficiency benefits of a hopping system. Here we show a real-time, computationally efficiency, non-linear drag compensated, trajectory generation methodology and accompanying Lyapunov-based controller. The combined system can create and follow complex aerial trajectories from liftoff to touchdown on horizontal and vertical surfaces, while maintaining strick control over the orientation at touchdown. The computational efficiency provides broad applicability across all size scales of hopping robots while maintaining applicability to quadrotors in general.

cs.RO↗

arXiv2024

Optimized Kalman Filter based State Estimation and Height Control in Hopping Robots

Rotor-based hopping locomotion significantly improves efficiency and operation time as compared to purely flying systems; where most hopping robots use the liftoff states and an assumed ballistic trajectory to determine the hopping height. However, significant aerial phase force (e.g., thrust and drag) can invalidate this assumption and lead to poor estimation performance. To combat this issue, a group has implemented multiple sensors (active and passive optical, inertial, and contact) and significant computational power to achieve full state estimation. This, however, poses a significant challenge to the development of light-weight, high-performance, low observable, jamming and electronic interference resistant hopping systems; especially in perceptually degraded environments (e.g., dust, smoke). Here we show a training procedure for a coupled hopping phase and Kalman filter-based vertical state estimator, requiring only inertial measurements, which is able to learn the characteristics of the target system, sensors, locomotion behaviors, environment, and acceleration measurement aliasing conditions. The resulting estimator, given hop heights up to 4 m and velocities up to $\pm7$ m/s, achieves a mean absolute percent error in the hop apex height of 12.5% with an aerial trajectory average normalized mean absolute error in position and velocity of 19% and 16.5%, respectively; while operating at 840 Hz, on a dual-core 240 MHz processor, with a total robot mass of 672 g. Due to the low mass and computational power, the presented estimator could also be used as a degraded operational mode in cases of sensor damage, malfunction, or occlusion in more complex robots.

cs.RO↗

arXiv2023

Design and Control of a High-Performance Hopping Robot

Jumping and hopping locomotion are efficient means of traversing unstructured rugged terrain with the former being the focus of roboticists; a focus that has recently been changing. This focus has led to significant performance and understanding in jumping robots but with limited practical applications as they require significant time between jumps to store energy, thus relegating jumping to a secondary role in locomotion. Hopping locomotion, however, can preserve and transfer energy to subsequent hops without long energy storage periods. However, incorporating the performance observed in jumping systems into their hopping counterparts is an ongoing challenge. To date, hopping robots typically operate around 1 meter with a maximum of 1.63 m whereas jumping robots have reached heights of 30 m. This is due to the added design and control complexity inherent in developing a system able to input and store the necessary energy while withstanding the forces involved and managing the system's state. Here we report hopping robot design principles for efficient, robust, high-specific energy, and high-energy input systems through analytical, simulation, and experimental results. The resulting robot (MultiMo-MHR) can hop over 4 meters ($\sim$2.4x the current state-of-the-art) and is designed to withstand impact at terminal velocity ($\geq 30.7$ m).

cs.RO↗

arXiv2018

Musical Chair: Efficient Real-Time Recognition Using Collaborative IoT Devices

The prevalence of Internet of things (IoT) devices and abundance of sensor data has created an increase in real-time data processing such as recognition of speech, image, and video. While currently such processes are offloaded to the computationally powerful cloud system, a localized and distributed approach is desirable because (i) it preserves the privacy of users and (ii) it omits the dependency on cloud services. However, IoT networks are usually composed of resource-constrained devices, and a single device is not powerful enough to process real-time data. To overcome this challenge, we examine data and model parallelism for such devices in the context of deep neural networks. We propose Musical Chair to enable efficient, localized, and dynamic real-time recognition by harvesting the aggregated computational power from the resource-constrained devices in the same IoT network as input sensors. Musical chair adapts to the availability of computing devices at runtime and adjusts to the inherit dynamics of IoT networks. To demonstrate Musical Chair, on a network of Raspberry PIs (up to 12) each connected to a camera, we implement a state-of-the-art action recognition model for videos and two recognition models for images. Compared to the Tegra TX2, an embedded low-power platform with a six-core CPU and a GPU, our distributed action recognition system achieves not only similar energy consumption but also twice the performance of the TX2. Furthermore, in image recognition, Musical Chair achieves similar performance and saves dynamic energy.

cs.CV↗