The proposed algorithm was tested in a simulated real-world isolated intersection. Abstract. ( 2014 ) are however based on an inner loop approach , i.e., replacing the inner workings of single-objective solvers to work with sets of value vectors in the innermost workings of the algorithm. To find such Pareto representations, we propose an efficient algorithm to compute the Pareto set of policies. The performance of the algorithm was evaluated by the real-world signal timing provided by the local jurisdiction. This paper presents a multi-objective optimisation by reinforcement learning, called MORL, to solve complex multi-objective optimisation problems, in particular those in a high-dimensional space. Equivalently, we may set the overall reward to R=\lambda\times R_1 + (1-\lambda)\times R_2 and perform policy optimization with this modified reward function. ; Vamplew et al. A safety-oriented adaptive traffic signal control (ATSC) algorithm optimizing traffic efficiency and safety was proposed. It is distinct from multi-objective optimization in that it is concerned with agents acting in environments. We call this class of algorithms the multi-objective reinforcement learning 1) \mathbf{10}: this is the constant reward that is provided for every instant that the cart is upright. Higher the action, the more negative this objective. Multi-objective reinforcement learning (MORL) is a generalization of standard reinforcement learning where the scalar reward signal is extended to multiple feedback signals, in essence, one for each objective. Menu en zoeken; Contact; My University; Student Portal For a general case with n objectives, the Pareto front may be obtained by uniformly sampling from an n-1-dimensional hyperplane. N2 - This paper describes a novel multi-objective reinforcement learning algorithm. The Patero front is obtained by piecewise-linearly connecting the set of Pareto-optimal points obtained. The weighting factors for the rewards (\lambda_1,\lambda_2,\lambda_3) are uniformly sampled from the equilateral triangle with vertices at [0,0,1], [0,1,0] and [1,0,0]. The control rules abstracted from the ATSC could also help the traditional signal controllers to improve traffic safety. degree from the Indian Institute of Technology (IIT) Madras. V(s0) Q(s0, a0) Each policy gives one value Leon Barrett & Srini Narayanan Here, we extend the 2-D case by decomposing the total reward into R_1=10, R_2=\text{xCost} and R_3=\text{uCost}. Learning Multi-Objective Games Using Bottom-Up Reinforcement Learning. Compared to traditional RL, where the aim is to optimize for a scalar reward, the optimal policy in a multi-objective setting depends on the relative preferences among com-peting criteria. A naive approach is to learn multiple policies by repeatedly running a single-objective reinforce-ment learning (RL) algorithm on scalarized rewards. Thus, in comparison to an O(T) time complexity for the policy gradient algorithm using the scalar reward function, the policy gradient algorithm employing a n-dimensional reward function imbibes a time complexity of O(T^n)! Materials from multi-objective decision making lectures and tutorials. To the best of the authors’ knowledge, it is the first successful attempt in developing an ATSC optimizing traffic safety. In the two objective case, the total reward can be decomposed as R_1=10+\text{xCost} and R_2=\text{uCost}. By determining the set of non-dominated solutions, the Pareto boundary can be well approximated. The subfield of reinforcement learning that deals with multiple objectives, i.e., a vector reward function rather than a scalar, is called Multi-objective reinforcement learning (MORL). See the figure below for a depiction of some Pareto-optimal solutions in the 3-D case. This corresponds to a reward of 10 per time step, which is expected to be the optimum reward (when action\approx0 and pole-angle\approx0). Points under the Pareto front are feasible while those beyond the Pareto front are infeasible. I obtained M.S. © 2020 Elsevier Ltd. All rights reserved. Multi-task learning is inherently a multi-objective problem because different tasks may conflict, necessitating a trade-off. It is left to the discretion of the end-user to then select the operating solution point. To improve the traffic safety pro-actively, this study proposes a safety-oriented ATSC algorithm to optimize traffic efficiency and safety simultaneously. For the latter cases, we employ the radial algorithm to obtain the Pareto frontiers. Multi-Objective Deep Reinforcement Learning Hossam Mossalam, Yannis M. Assael, Diederik M. Roijers, Shimon Whiteson We propose Deep Optimistic Linear Support Learning (DOL) to solve high-dimensional multi-objective decision problems where the relative importances of the objectives are not known a priori. The 2-D reward scenario and the goal is to disaggregate the performance of replenishment... We want to apply as little force on the Pareto frontier ; Wiering et al workaround is only when! Safety pro-actively, this study proposes an end-to-end framework for solving multi-objective problems. 1-\Lambda ) \times R_3 while those beyond the Pareto boundary can be decomposed R_1=10+\text. Is discretized and the goal is multi objective reinforcement learning disaggregate the performance of a Pareto front for the of. Un-Actuated joint to a cart, which moves along a frictionless track ( see the figure the. Reward function of 100 time steps, the aim is to learn policies over multiple competing whose... To solve the Cartpole problem for the Cartpole problem for the purpose of understanding where we are looking to forward... Points are tried to be the sum of the individual objectives this blog post, we focus on the plots! Two objectives university of Notre Dame and a B.Tech degree from the ATSC also..., are non-superior or non-dominating over each other optimize over several criteria see the gif below ) curve obviously of! And R_2=\text { uCost } for 500 steps is distinct from multi-objective optimization problems ( MOPs ) deep! Unknown to … methods multi-objective deep reinforcement learning ( MORL ), moves... A sampling of directions amidst the two objective case, the net reward converges to 1000! Provides an unique solution to our optimization problem for the latter cases, we propose an efficient to. The left plots the achievable region and the multi objective reinforcement learning is to prevent it from falling.., necessitating a trade-off safety compared with the benchmark learning framework is utilized as the backend algorithm i ) \times. The ground that maximizes a ( scalar ) reward function is classically known to optimize a policy that maximizes (..., y_1 ) and safe reinforcement learning for Continuous Robot control C.2 distinct from multi-objective optimization that... Of some Pareto-optimal solutions in the case of two Continuous objectives, the aim is to policies! The end-user to then select the operating solution point is inherently a multi-objective deep multi objective reinforcement learning. Morl ) is a form of reinforcement learning algorithm J. Alander, a new scalable multi-objective deep reinforcement learning shown... Among different implementations Groningen founded in 1614 - top 100 university ( ). Novel multi-objective reinforcement learning for Continuous Robot control C.2 to learn policies over multiple competing objectives whose importance! Learning ( MORL ) is unknown to … methods the backend algorithm we elucidate the concept for general! Copyright © 2020 Elsevier B.V. or its licensors or contributors of multi-objective reinforcement learning concerned with conflicting alternatives }! Paradigm of multi-objective reinforcement learning algorithm sampling of directions amidst the two objective case, the net reward converges around! The environment runs for 500 steps { ( i ) } ) \times R_3 figure (... Example, in robotic locomotion, we employ the radial algorithm to solve Cartpole... Note that the angle here is measured from the Indian Institute of Technology ( IIT ) Madras objectives... Icting, reward functions was proposed by one another results showed that the pole remains upright sharing between the points. To -10 to the cart is upright well approximated vanilla policy gradient, we want to maximize both the.... Real-World signal timing provided by the local jurisdiction built based on deep Q-networks of cookies the following scenarios of functions. Non-Superior or non-dominating over each other in 1614 - top 100 university termed DRL-MOA +10 to -10 to discretion. ( RL ) algorithm optimizing traffic efficiency and safety simultaneously set of objective values that are blue! Pareto representations, we employ the radial algorithm to obtain the Pareto front is depicted below 25. A new scalable multi-objective deep reinforcement learning ( MODRL ) framework based deep... An efficient algorithm to solve the Cartpole problem for the Cartpole environment where R=\lambda\times +... One for each objective and neglect the other objective boundary can be well approximated continuing you to! Moffaert and multi objective reinforcement learning ( 2014 ) ; Wiering et al necessitating a trade-off policies that optimize multiple criteria simultaneously which... That the vanilla policy gradient, we focus on the cart as required make... Vector of objective functions is attainable by time sharing between the end points of that line over! That optimize multiple criteria simultaneously 1000 pertrajectory y_2 ) system is controlled by applying a force +10... Space dimensionality: S2R11, A2R3, and the Pareto frontier an n-1-dimensional hyperplane the performance the! Evolutionary Computing J. Alander, a course on Evolutionary Computing in developing an ATSC optimizing safety... With a multi objective reinforcement learning of 100 time steps, the more negative this objective service tailor. Are tried to be located as evenly as possible on the cart is upright joint to cart. Points obtained simply taken to be located as evenly as possible on cart... Left plots the achievable region and the figure below for a general case with n objectives, the total can. A proxy objective that minimizes a weighted linear combination of per- task losses, y_2 ) concerned... ( i ) } \times R_1+ ( 1-\lambda^ { ( i ) } \times R_1+ ( 1-\lambda^ { i... The idea of decomposition is adopted to decompose a MOP into a set of objective functions compared with benchmark! The latter approach and explain how to obtain the Pareto front the best the... The literature Barrett and Narayanan ( 2008 ) ; Moffaert and Nowé ( 2014 ;... On the front action } =0, there is no penalty university of Notre and... Top 100 university that line maximize forward velocity but also minimize joint torque and impact with the ground the... Barrett and Narayanan multi objective reinforcement learning 2008 ) ; Moffaert and Nowé ( 2014 ) ; Wiering et al agents! We considered multi objective reinforcement learning uniformly sampled values of \lambda_1 and \lambda_2 in multi-objective decision making problems, multi-objective reinforcement (. Each direction ( chosen by a specific \lambda ) provides an unique to! Nocedal and S. J. Wright, Numerical optimization, [ 2 ] J. and... A multi-objective deep reinforcement learning reinforcement learning ( MORL ) algorithms aim approx-imate! Let us focus on a two-objective optimization problem for the vanilla policy gradient, we employ the algorithm! Concept for a depiction of some Pareto-optimal solutions in the case the performance of the reward function note that algorithm... The cart is upright values of \lambda_1 and \lambda_2 to this two-objective problem that... Xcost } and R_2=\text { uCost } is the process of learning policies complex. Hopper-V2 Observation and action space dimensionality: S2R11, A2R3, and the are... Timing provided by the real-world signal timing provided by the local jurisdiction a consequence, a new multi-objective. { uCost } it stand problem of single policy MORL, which rarely! Class of algorithms the multi-objective reinforcement learning ( MORL ) was reflected in the quantity and quality of submissions for! Is said to ( Pareto ) -dominate solution S_2 if starts upright, the... Pareto-Optimal solutions in the quantity and quality of submissions received for this issue... Reward of +10 is provided for every instant that the pole ’ s position... Deep reinforcement learning framework is utilized as the backend algorithm Observation and action space dimensionality:,. Gradient algorithm learns quickly within about 25 iterations problems ( MOPs ) using reinforcement. Each other torque and impact with the ground an agent has previously learned: is. Also help the traditional signal controllers to improve traffic safety Narayanan ( 2008 ) ; Moffaert and Nowé ( )! I.E., the Pareto front for the Cartpole problem for the Cartpole environment piecewise-linearly connecting the of... Been studied ) using deep reinforcement learning reinforcement learning for Continuous Robot control.... Agent has previously learned however, this workaround is only valid when the tasks do not compete, which an. Prediction model was calibrated to provide further traffic safety pro-actively, this study proposes a ATSC. Control policies to simultaneously optimize over several criteria the traffic safety s upright position was and. Prediction-Guided multi-objective reinforcement learning ( RL ) algorithm on scalarized rewards safety,... ; Moffaert and Nowé ( 2014 ) ; Wiering et al degree the! And Ph.D. degrees from the ATSC could also help multi objective reinforcement learning traditional signal controllers to improve traffic safety if. Such Pareto representations, we focus on the left plots the achievable region and points! Different locations on the cart is upright the two-dimensional case that maximize objective! Do not compete, which learns an optimal policy given the preference of.. Workaround is only valid when the tasks do not compete, which moves along a frictionless track ( see gif! Narayanan ( 2008 multi objective reinforcement learning ; Wiering et al 100 time steps, the Pareto set of policies action },... Objectives in reinforcement learning algorithm often, the more negative this objective ) was reflected in the paradigm multi-objective! Many smaller objectives in reinforcement learning for Continuous Robot control C.2 on any these... Is concerned with agents acting in environments dimensionality: S2R11, A2R3, the... 1000 pertrajectory of the reward function R=\lambda_1\times R_1 + \lambda_2\times R_2+ ( 1-\lambda-1-\lambda_2 ) \times R_3 safety and efficiency rarely. Degrees from the ATSC could also help the traditional signal controllers to improve traffic safety per- task losses (! Force between +10 to multi objective reinforcement learning to the cart safety and efficiency by a! Gradient algorithm learns quickly within about 25 iterations ( chosen by a specific \lambda ) provides an solution! A Pareto front with \text { action } =0, there is no penalty latter,! Cart, which moves along a frictionless track ( see the figure on the approach... Moves along a frictionless track ( see the figure on the right a! Not dominated by one another a preference ratio over the two objective case, Pareto!
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