Reinforcement Learning's Influence to Robotics Development

Reinforcement learning has become a promising and effective method to solve robots' complex control problems, enabling agents to learn optimal behaviors independently in a dynamic, uncertain, and usually high-dimensional environment. This paper comprehensively reviews the latest progress in applying reinforcement learning technology in robotics, paying special attention to key areas such as path planning, dynamic obstacle avoidance, multi-robot cooperation, and human-computer interaction. By critically analyzing various methods based on reinforcement learning, this paper emphasizes the key progress in improving robot autonomy, decision-making, and adaptability. It also discusses the challenges of deploying reinforcement learning in real-world robot applications, including sample efficiency, security, scalability, and generalization to new environments. In particular, Deep Reinforcement Learning (DRL) shows great potential in enhancing the robot's ability, especially in a complex, unstructured environment. However, challenges such as high computing costs and long training time still need to be addressed. Finally, the paper suggests that future research should focus on the hybrid RL method, improve learning efficiency, combine domain knowledge, and combine RL with other advanced technologies such as computer vision, multi-agent system, and real-time feedback mechanism, to further expand its potential application and increase its influence in the field of robotics.

In robotics, the ultimate goal of reinforcement learning is to endow robots with the ability to learn, improve, adapt and reproduce tasks with dynamically changing constraints based on exploration and autonomous learning. We give a summary of the state-of-the-art of reinforcement learning in the context of robotics, in terms of both algorithms and policy representations. Numerous challenges faced by the policy representation in robotics are identified. Three recent examples for the application of reinforcement learning to real-world robots are described: a pancake flipping task, a bipedal walking energy minimization task and an archery-based aiming task. In all examples, a state-of-the-art expectation-maximization-based reinforcement learning is used, and different policy representations are proposed and evaluated for each task. The proposed policy representations offer viable solutions to six rarely-addressed challenges in policy representations: correlations, adaptability, multi-resolution, globality, multi-dimensionality and convergence. Both the successes and the practical difficulties encountered in these examples are discussed. Based on insights from these particular cases, conclusions are drawn about the state-of-the-art and the future perspective directions for reinforcement learning in robotics.

Common challenges in the area of robotics include issues such as sensor modeling, dynamic operating environments, and limited on-broad computational resources. To improve decision making, robots need a dependable framework to facilitate communication between different modules and the optimal action for real-world applications. The Robotics Operating System (ROS) and Reinforcement Learning (RL) are two promising approaches that help accomplish precise control, seamless integration of sensors-actuators, and exhibit learned behavior. The ROS enables seamless communication between heterogeneous components, while RL focuses on learning optimal behaviors through trial-and-error scenarios. Combining the ROS and RL offers superior decision making, improved perception, enhanced automation, and reliability. This work focuses on investigating ROS-based RL applications across various domains, aiming to enhance understanding through comprehensive discussion, analysis, and summarization. We base our evaluation on the application area, type of RL algorithm used, and degree of ROS–RL integration. Additionally, we provide summary of seminal works that define the current state of the art, along with GitHub repositories and resources for research purposes. Based on the review of successfully implemented projects, we make recommendations highlighting the advantages and limitations of RL techniques for specific applications and environments. The ultimate goal of this work is to advance the robotics field by providing a comprehensive overview of the recent important works that incorporate both the ROS and RL, thereby improving the adaptability of these emerging techniques.

Technological advancements in robotics and cognitive science are contributing to the development of the field of cognitive robotics. Modern robotic platforms are able to exhibit the ability to learn and reason about complex tasks and to follow behavioural goals in complex environments. Nevertheless, many challenges still exist. One of these great challenges is to equip these robots with cognitive systems that allow them to deal with less constrained situations, beyond constrained scenarios as in industrial robotics. In this work we explore the application of the Reinforcement Learning (RL) paradigm to study the autonomous development of robot controllers without a priori supervised learning. Such a model-based RL architecture is discussed for the cognitive implications of applying RL in humanoid robots. To this end we show a developmental framework for RL in robotics and its implementation and testing for the iCub robotic platform in two novel experimental scenarios. In particular we focus on iCub simulation experiments with comparisons between internal perception-based reward signals and external ones, in order to compare learning performance of the robot guided by its own perception of action's outcomes with the one when the robot has its actions externally evaluated.

Reinforcement learning holds the promise of enabling autonomous robots to learn behavioural skills with minimal human intervention. Reinforcement learning in robotics allows designing an algorithm that makes a robot learn a specific task by itself and arrive at an optimal policy that accomplishes its task without being specifically programmed to do so. This paper demonstrates the approach of using Deep reinforcement Learning in Teaching a quadruped robot how to walk, without programming it specifically to do so, and how to utilize the ability of self-learning robots in fault adaptive control algorithm based on reinforcement learning to teach the robot to adapt to faults and accomplish its mission.

Introduction Reinforcement learning formalizes the concept of learning from interactions.1 Broadly, reinforcement learning focuses on a setting in which an agent (decision maker) sequentially interacts with an environment that is partially unknown to them. At each stage, the agent takes an action and receives a reward. The objective of the agent is to maximize rewards accumulated in the long run. There are many situations in health care where decisions are made sequentially for which reinforcement learning approaches could prove useful for decision making. Throughout this article, we consider treatment prescription as an archetypical example to connect reinforcement learning concepts to a health care setting. In this setting, the care provider, the prescribed treatment, and the patients can be viewed as the agent, the action, and the environment, respectively, as depicted in Figure 1.Figure 1: Sequential treatment of AKI or CKD complications modeled as a reinforcement learning problem.Background In this section, with the objective of making reinforcement learning literature more accessible to a clinical audience, we briefly introduce related fundamental concepts and approaches. We refer the interested reader to Sutton and Barto1 for a comprehensive introduction to reinforcement learning. Markov Decision Processes Markov decision processes (MDPs) are a formalism of the sequential decision-making problem that has been central to the theoretical and practical advancements of reinforcement learning. In each stage of an MDP, the agent observes the state of the environment and takes an action, which, in turn, results in a change of the state. This change of state is assumed to be probabilistic with the next state being determined only by the preceding state, the chosen action, and the transition probability. The agent also receives a reward that is a function of the taken action, the preceding state, and the subsequent state. In an MDP, the objective of the agent is to maximize the return defined as the reward accumulated over a time horizon. In some applications, it is common to consider the horizon to be infinite, in which case the future rewards are discounted by a factor smaller than one. The selection of action by the agent on the basis of the observed state is known as the policy. More formally, a policy is a probabilistic mapping from states to each possible action. Because the policy and the reward are a function of the state, it is critical to estimate the utility of being in a certain state. More specifically, the value function is defined as the expected return starting from a given state under the chosen policy. Under this formalism, the objective of the agent is to find the optimal policy that maximizes the value function for all states. Reinforcement Learning Methods Action-value methods are a class of reinforcement learning methods in which the actions are chosen on the basis of the estimation of their long-term value. A prominent example of an action-value method is Q-learning in which the agent iteratively takes actions with the highest estimated values and updates the action-state value function on the basis of new observations. Policy gradient methods are another class of reinforcement learning methods that seek to optimize the policy directly instead of choosing actions on the basis of their respective estimated value. Such methods could be advantageous in health care applications that entail a large number of possible actions, e.g., when recommending a wide range of drug dosages or treatment options. Clinical Applications Reinforcement learning frameworks and methods are broadly applicable to clinical settings in which decisions are made sequentially. A prominent clinical application of reinforcement learning is for treatment recommendation, which has been studied across a variety of diseases and treatments including radiation and chemotherapy for cancer, brain stimulation for epilepsy, and treatment strategies for sepsis.2–5 In such treatment recommendation settings, a policy is commonly known as a dynamic treatment regime. There are various other clinical applications of reinforcement learning including diagnosis, medical imaging, and decision support tools (see refs. 2–5 and the references therein). Reinforcement Learning in Nephrology Although there have been recent applications of machine learning in nephrology,6,7 to the best of the authors' knowledge, the application of reinforcement learning to nephrology has been primarily limited to optimizing the erythropoietin dosage in hemodialysis patients.8,9 However, there are other settings where reinforcement learning has the potential to improve patient care in nephrology. For example, reinforcement learning methods can be adopted in the treatment of the complications of AKI or CKD (Figure 1). In this problem, the state models the conditions of the patient (e.g., vital signs, laboratory test results including urine and blood tests, and urine output measurements). The action refers to the treatment options (e.g., the dosage of medications such as sodium polystyrene sulfonate, and hemodialysis). The reward models the improvement in patient conditions. Similarly, reinforcement learning can help automate and optimize the dosage of immunosuppressive drugs in kidney transplants. Challenges and Opportunities Despite the success of reinforcement learning in several simplified clinical settings, their large-scale application to patient care faces several open challenges. The complexity of human biology complicates modeling clinical decision making as a reinforcement learning problem. The state space in such settings is often enormous, which could make a purely computational approach infeasible. Moreover, modeling all potential objectives a priori as a reward function may not be feasible. To overcome these challenges and realize the potential of reinforcement learning, clinical insight can play a pivotal role. More specifically, restricting the state space to only include highly relevant clinical variables could greatly reduce the computational complexity. Furthermore, using inverse reinforcement learning,2 relevant reward functions can be learned from retrospective studies assuming the optimality of clinical decisions. Another critical challenge is addressing moral and ethical concerns. It is imperative to ensure that reinforcement learning methods do not cause harm to the patient. To this end, there exists a need for a thorough validation of such methods before their use in patient care. Hence, there is a need to go beyond retrospective studies that have been used for the proof of concept of most existing reinforcement learning methods in health care applications.2,3 The lessons learned from the success of reinforcement learning in other application areas (e.g., self-driving cars) can help navigate the path to realizing its potential in health care. Accessible open-source simulation environments that enable researchers to compare various approaches are essential to the field of reinforcement learning. OpenAI Gym is currently the leading toolkit containing a wide range of simulated environments, e.g., surgical robotics.10 The development of high-quality and reliable simulation environments for nephrology and other health care applications can facilitate the development and validation of reinforcement learning methods beyond limited retrospective studies. The adoption of methods validated in such simulation environments in actual clinical settings will require clinicians' oversight. Similar to how self-driving cars require a human driver to ensure collision avoidance, clinicians' oversight is critical to ensure the safety of the patients, especially in the early stages of the adoption of reinforcement learning methods. The data from clinicians' decisions (e.g., overruling the automated treatment recommendation) can be used to improve the reliability of autonomous systems over time and reduce the burden of clinicians' oversight.

Reinforcement Learning in Robotics: A Survey

This paper proposes an innovative deep learning algorithm, denominated as Neuroevolution of Hybrid Neural Networks in a Robotic Agent (NRNH-AR). This algorithm stands out in computational efficiency, evolutionary stability, and classification speed, surpassing other existing methods such as FAM-HGNN, I3A, DQN, among others. The triptych design of the NRNH-AR optimizes resource usage and exhibits superior adaptability in dynamic environments, which is a critical factor in robotics. The integration of artificial vision techniques enhances the capability for rapid classification of observations. Throughout 300 epochs in a dynamic environment, the importance of a minimal database for the algorithm’s effective evolution was evidenced. Moreover, it was found that the accuracy of the Convolutional Neural Network (CNN) directly impacts the performance of the NRNH-AR. An additional study of 850 epochs in a static environment provided a deeper understanding of the evolution and adaptation of learning networks. The NRNH-AR is positioned as a viable and promising solution in the field of applied deep learning in robotics.

The widespread deployment of smart meters and communication technologies brings opportunities to improve the adaptability and flexibility of future manufacturing systems under growing complexity and uncertainty. As a result, data-driven approaches, especially Reinforcement Learning (RL) methods, are gaining wide attention in recent years. Although in the current literature, RL approaches show superiority over traditional methods in many applications, a comprehensive review and comparison of different RL methods and their use in discrete manufacturing system control under changing environments have not yet been established. This paper first provides a literature review of RL algorithms for decision-making in discrete manufacturing systems, and then systematically discusses the underlying mechanisms of four most commonly used RL algorithms. In addition, the performance of these RL algorithms is compared by solving a production control problem, which aims to maximize the profit under time-varying production costs. The comparison results show that the single-agent RL methods with discrete action space can provide satisfactory results in small-scale systems, while multi-agent RL algorithms are more suitable to solve problems in complex, large-scale systems to remit the curse of dimensionality. This research sheds light on the impacts of RL method selection on the search for high-quality solutions in manufacturing systems, which is envisioned to drive future research on RL-supported manufacturing systems.

The paper does not provide any original contribution. Therefore, it cannot be considered a research paper. No results are included. If it is supposed to be a review article, then it is poorly written. The paper should be rejected.

Robust Deep Reinforcement Learning in Robotics via Adaptive Gradient-Masked Adversarial Attacks

Reinforcement learning (RL) has shown promising performance in autonomous driving applications in recent years. The early end-to-end RL method is usually unexplainable and fails to generate stable actions, while the hierarchical RL (HRL) method can tackle the above issues by dividing complex problems into multiple sub-tasks. Prior HRL works either select discrete driving behaviors with continuous control commands, or generate expected goals for the low-level controller. However, they typically have strong scenario dependence or fail to generate goals with good quality. To address the above challenges, we propose a Continuous-Lattice Hierarchical RL (Cola-HRL) method for autonomous driving tasks to make high-quality decisions in various scenarios. We utilize the continuous-lattice module to generate reasonable goals, ensuring temporal and spatial reachability. Then, we train and evaluate our method under different traffic scenarios based on real-world High Definition maps. Experimental results show our method can handle multiple scenarios. In addition, our method also demonstrates better performance and driving behaviors compared to existing RL methods.

Adaptive bitrate (ABR) streaming algorithms play an important role in ensuring a high Quality of Experience (QoE) for the consumer. However, a lot of ABR algorithms tend to be too ad hoc. In response, methods based on a Markov Decision Process (MDP) offer more intelligent models. In particular, Reinforcement Learning (RL) methods typically do so via QoE metrics. However, RL methods are plagued by high complexity and long convergence times due to their model-free nature. This paper proposes qMDP, which is an RL method with an MDP partially modeled by an M/D/1/K queue. Our study shows that qMDP results in higher QoE and faster convergence compared to a QoE-only model-free version.

This paper describes a new class of autonomous intelligent systems for robot navigation application focusing on the synthesis, analysis and discussion of the learning process. Systems in this class are able to learn independently of supervision. In fact, they learn interacting with the environment while exploring it. A reinforcement learning strategy (inspired on the classical animal conditioning) and Hebb-like rule learning mechanisms support the knowledge acquisition process. The intelligent system must learn navigate the robot in an unknown environment, guiding it to targets according to a safe trajectory (without collisions). Their modular and hierarchical architecture is based on fuzzy systems and neural network techniques. The proposed approach has been validated by using a simulator and a mobile robot. In both cases, the experiments show that the autonomous intelligent system has a clear evidence of independent learning capability and exhibits a good performance during the navigation. Furthermore, this approach is compared with other system where there is no intelligent mechanisms to guide the robot.

Reinforcement learning (RL) for robotics is challenging due to the difficulty in hand-engineering a dense cost function, which can lead to unintended behavior, and dynamical uncertainty, which makes exploration and constraint satisfaction challenging. We address these issues with a new model-based reinforcement learning algorithm, Safety Augmented Value Estimation from Demonstrations (SAVED), which uses supervision that only identifies task completion and a modest set of suboptimal demonstrations to constrain exploration and learn efficiently while handling complex constraints. We then compare SAVED with 3 state-of-the-art model-based and model-free RL algorithms on 6 standard simulation benchmarks involving navigation and manipulation and a physical knot-tying task on the da Vinci surgical robot. Results suggest that SAVED outperforms prior methods in terms of success rate, constraint satisfaction, and sample efficiency, making it feasible to safely learn a control policy directly on a real robot in less than an hour. For tasks on the robot, baselines succeed less than 5% of the time while SAVED has a success rate of over 75% in the first 50 training iterations. Code and supplementary material is available at https://tinyurl.com/saved-rl.