Online Gain Adaptation of Whole-Body Control for Legged Robots with Unknown Disturbances

This paper proposes an online gain adaptation approach to enhance the robustness of whole-body control (WBC) framework for legged robots under unknown external force disturbances. Without properly accounting for external forces, the closed-loop control system incorporating WBC may become unstable, and therefore the desired task goals may not be achievable. To study the effects of external disturbances, we analyze the behavior of our current WBC framework via the use of both full-body and centroidal dynamics. In turn, we propose a way to adapt feedback gains for stabilizing the controlled system automatically. Based on model approximations and stability theory, we propose three conditions to ensure that the adjusted gains are suitable for stabilizing a robot under WBC. The proposed approach has four contributions. We make it possible to estimate the unknown disturbances without force/torque sensors. We then compute adaptive gains based on theoretic stability analysis incorporating the unknown forces at the joint actuation level. We demonstrate that the proposed method reduces task tracking errors under the effect of external forces on the robot. In addition, the proposed method is easy-to-use without further modifications of the controllers and task specifications. The resulting gain adaptation process is able to run in real-time. Finally, we verify the effectiveness of our method both in simulations and experiments using the bipedal robot Draco2 and the humanoid robot Valkyrie.

Closed-Loop Control of a New High Step-Up Multi-Input Multi-Output DC-DC Converter

A new multi-input multi-output dc-dc converter with high step-up capability for wide power ranges is proposed in this paper. The converter's number of inputs and outputs is arbitrary and independent of each other. The proposed topology combines the benefits of DC-DC boost and switched-capacitor converters. The number of input, output, and voltage multiplier stages is arbitrary and depends on the design conditions. First, the various operating modes of the proposed converter are discussed. The closed-loop control system also must be designed using state space representation and small-signal modelling. Finally, the operation of the proposed converter is derived from the simulation results. Keywords: High power converter, Low voltage stress, Multi-Input Multi-Output (MIMO) converter, Non-isolated high step-up dc-dc converter, closed loop control.

Closing the Loop: Implementing Real-time Audio Feedback Systems in Musical Robots

<p>A closed-loop control system is any configuration that feeds information about its output back into the control stream. These types of systems have been in use for hundreds of years in various engineering related disciplines to carry out operations such as keeping rooms at the correct temperature, implementing cruise control in cars, and precisely positioning industrial machinery. When a musician performs a piece, a type of biological closed loop is invoked in which the player continuously listens to the sound of their instrument, and adjusts their actions in order to ensure their performance is as desired. However, most musical robots do not possess this ability, instead relying on open-loop systems without feedback. This results in the need for much manual intervention from the operators of these robots, unintuitive control interfaces for composing and performing music with them, and tuning, timing, dynamics and other issues occurring during performances. This thesis investigates applying closed-loop audio feedback techniques to the creation of musical robots to equip them with new expressive capabilities, interactive applications, musical accuracy, and greater autonomy. In order to realise these objectives, following an investigation of the history of musical automata and musical robotic control systems, several new robotic musical instruments are developed based on the principals of utilising embedded musical information retrieval techniques to allow the instruments to continuously ‘listen’ to themselves while they play. The mechanical and electronic systems and firmware of a closed-loop glockenspiel, a modular unpitched percussion control system, and a robotic chordophone control system are described in detail, utilising new software and hardware created to be accessible to electronic artists. The novel capabilities of the instruments are demonstrated both through quantitative evaluations of the performance of their subsystems, and through composing original musical works specifically for the instruments. This paradigm shift in musical robotic construction paves the way for a new class of robots that are intuitive to use, highly accurate and reliable, and possess a unique level of musical expressiveness.</p>

Closing the Loop: Implementing Real-time Audio Feedback Systems in Musical Robots

<p>A closed-loop control system is any configuration that feeds information about its output back into the control stream. These types of systems have been in use for hundreds of years in various engineering related disciplines to carry out operations such as keeping rooms at the correct temperature, implementing cruise control in cars, and precisely positioning industrial machinery. When a musician performs a piece, a type of biological closed loop is invoked in which the player continuously listens to the sound of their instrument, and adjusts their actions in order to ensure their performance is as desired. However, most musical robots do not possess this ability, instead relying on open-loop systems without feedback. This results in the need for much manual intervention from the operators of these robots, unintuitive control interfaces for composing and performing music with them, and tuning, timing, dynamics and other issues occurring during performances. This thesis investigates applying closed-loop audio feedback techniques to the creation of musical robots to equip them with new expressive capabilities, interactive applications, musical accuracy, and greater autonomy. In order to realise these objectives, following an investigation of the history of musical automata and musical robotic control systems, several new robotic musical instruments are developed based on the principals of utilising embedded musical information retrieval techniques to allow the instruments to continuously ‘listen’ to themselves while they play. The mechanical and electronic systems and firmware of a closed-loop glockenspiel, a modular unpitched percussion control system, and a robotic chordophone control system are described in detail, utilising new software and hardware created to be accessible to electronic artists. The novel capabilities of the instruments are demonstrated both through quantitative evaluations of the performance of their subsystems, and through composing original musical works specifically for the instruments. This paradigm shift in musical robotic construction paves the way for a new class of robots that are intuitive to use, highly accurate and reliable, and possess a unique level of musical expressiveness.</p>

A smart mask for active defense against airborne pathogens

Face masks are a primary preventive measure against airborne pathogens. Thus, they have become one of the keys to controlling the spread of the COVID-19 virus. Common examples, including N95 masks, surgical masks, and face coverings, are passive devices that minimize the spread of suspended pathogens by inserting an aerosol-filtering barrier between the user’s nasal and oral cavities and the environment. However, the filtering process does not adapt to changing pathogen levels or other environmental factors, which reduces its effectiveness in real-world scenarios. This paper addresses the limitations of passive masks by proposing ADAPT, a smart IoT-enabled “active mask”. This wearable device contains a real-time closed-loop control system that senses airborne particles of different sizes near the mask by using an on-board particulate matter (PM) sensor. It then intelligently mitigates the threat by using mist spray, generated by a piezoelectric actuator, to load nearby aerosol particles such that they rapidly fall to the ground. The system is controlled by an on-board micro-controller unit that collects sensor data, analyzes it, and activates the mist generator as necessary. A custom smartphone application enables the user to remotely control the device and also receive real-time alerts related to recharging, refilling, and/or decontamination of the mask before reuse. Experimental results on a working prototype confirm that aerosol clouds rapidly fall to the ground when the mask is activated, thus significantly reducing PM counts near the user. Also, usage of the mask significantly increases local relative humidity levels.

Automated Humidity Control System for Neonatal Incubator

Premature neonates are nursed in closed incubators to prevent transcutaneous water loss, dehydration, and excessive body cooling. These issues have serious risks that need to be eliminated by controlling the air’s relative humidity (RH) in the incubator. This paper aims to implement a closed-loop control system that maintains desired RH levels inside the incubator with an acceptable settling time and percentage. Designing the prototype is actuator-process-sensor based, and the implementation was in two main phases. First, building the incubator, which involved assembling the incubation space and the humidifier using a readily available ultrasonic piezoelectric transducer. Second, designing the control algorithm which is based on the ON/OFF algorithm with four levels of ON Humidification power. Finally, the results taken are the control system responses to a step input of desired values of relative humidity based on clinical guidance. Response results showed a maximum steady-state error of 2.5 and a minimum settling time of 0.8 min. The results indicate that the control system is fast and stable which meets the desired requirements. The designed control system is beneficial in reducing power usage and creating a safe humidification method for the infant.

Resilient adaptive event-triggered H∞ control for networked stochastic control systems under denial-of-service attacks

This paper addresses the problem of resilient adaptive event-triggered control (AETC) for networked stochastic control systems (NSCSs) in the presence of the external disturbance and the energy-constrained, nonperiodic denial-of-service (DoS) attacks. A novel adaptive event-triggered scheme (AETS) that considers the effect of the energy-constrained, nonperiodic DoS attacks on the communication network is proposed to reduce the usage of system resources and adapt the variation of the plant state, and the model of closed-loop control system is established in the framework of time-delay systems and switched systems. Then, based on the Lyapunov stability theory, the stability criterion and the co-design algorithm are derived, which are used to ensure that the closed-loop control system is stochastically exponentially stable (SES) with an [Formula: see text] disturbance attenuation performance and to implement the co-design of state-feedback controller and proposed AETS, respectively. Unlike the network-based [Formula: see text] control approach for NSCSs in the existing literature, the resilient adaptive event-triggered network-based [Formula: see text] control approach proposed in this paper not only can considerably save the usage of system resources, but also can be resilient towards the energy-constrained, nonperiodic DoS attacks. Finally, a resilient AETC for the F16 aircraft system shows the effectiveness and superiority of proposed strategy.