双Q网络学习的迁移强化学习算法

深度强化学习在训练过程中会探索大量环境样本,造成算法收敛时间过长,而重用或传输来自先前任务(源任务)学习的知识,对算法在新任务(目标任务)的学习具有提高算法收敛速度的潜力.为了提高算法学习效率,提出一种双Q网络学习的迁移强化学习算法,其基于actor-critic框架迁移源任务最优值函数的知识,使目标任务中值函数网络对策略作出更准确的评价,引导策略快速向最优策略方向更新.将该算法用于Open AI Gym以及在三维空间机械臂到达目标物位置的实验中,相比于常规深度强化学习算法取得了更好的效果,实验证明提出的双Q网络学习的迁移强化学习算法具有较快的收敛速度,并且在训练过程中算法探索更加稳定.     

神经网络增强学习的梯度算法研究

针对具有连续状态和离散行为空间的Markov决策问题，提出了一种新的采用多层前馈神经网络进行值函数逼近的梯度下降增强学习算法，该算法采用了近似贪心且连续可微的Boltzmann分布行为选择策略，通过极小化具有非平稳行为策略的Bellman残差平方和性能指标，以实现对Markov决策过程最优值函数的逼近，对算法的收敛性和近似最优策略的性能进行了理论分析，通过Mountain-Car学习控制问题的仿真研究进一步验证了算法的学习效率和泛化性能。     

The Effect of Representation and Knowledge on Goal-Directed Exploration with Reinforcement-Learning Algorithms

We analyze the complexity of on-line reinforcement-learning algorithms applied to goal-directed exploration tasks. Previous work had concluded that, even in deterministic state spaces, initially uninformed reinforcement learning was at least exponential for such problems, or that it was of polynomial worst-case time-complexity only if the learning methods were augmented. We prove that, to the contrary, the algorithms are tractable with only a simple change in the reward structure ("penalizing the agent for action executions") or in the initialization of the values that they maintain. In particular, we provide tight complexity bounds for both Watkins' Q-learning and Heger's Q-hat-learning and show how their complexity depends on properties of the state spaces. We also demonstrate how one can decrease the complexity even further by either learning action models or utilizing prior knowledge of the topology of the state spaces. Our results provide guidance for empirical reinforcement-learning researchers on how to distinguish hard reinforcement-learning problems from easy ones and how to represent them in a way that allows them to be solved efficiently.This research was supported in part by NASA under contract NAGW-1175. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of NASA or the U.S. government.     

Asynchronous Stochastic Approximation and Q-Learning

We provide some general results on the convergence of a class of stochastic approximation algorithms and their parallel and asynchronous variants. We then use these results to study the Q-learning algorithm, a reinforcement learning method for solving Markov decision problems, and establish its convergence under conditions more general than previously available.     

基于改进Q-学习算法的多阶段群体决策模型

多阶段群体决策问题是一类典型的动态群体决策问题,主要针对离散的确定状态下的最优群体决策问题求解.但由于现实环境面临的大部分是不确定状态空间,甚至是未知环境空间(例如状态转移概率矩阵完全未知),为了寻求具有较高共识度的多阶段群体最优策略,决策者需要通过对环境的动态交互来获得进一步的信息.针对该问题,利用强化学习技术,提出一种求解多阶段群体决策的最优决策算法,以解决在不确定状态空间下的多阶段群体决策问题.结合强化学习中的Q-学习算法,建立多阶段群体决策Q-学习基本算法模型,并改进该算法的迭代过程,从中学习得到群体最优策略.同时证明基于Q-学习得到的多阶段群体最优策略也是群体共识度最高的策略.最后,通过一个计算实例说明算法的合理性及可行性.     

基于改进深度强化学习的三维环境路径规划

提出一种改进深度强化学习算法(NDQN),解决传统Q-learning算法处理复杂地形中移动机器人路径规划时面临的维数灾难.提出一种将深度学习融于Q-learning框架中,以网络输出代替Q值表的深度强化学习方法.针对深度Q网络存在严重的过估计问题,利用更正函数对深度Q网络中的评价函数进行改进.将改进深度强化学习算法与...     

样本有限关联值递归Q学习算法及其收敛性证明

一个激励学习Agent通过学习一个从状态到动作映射的最优策略来解决问题，求解最优决策一般有两种途径：一种是求最大奖赏方法，另一种最求最优费用方法，利用求解最优费用函数的方法给出了一种新的Q学习算法，Q学习算法是求解信息不完全Markov决策问题的一种有效激励学习方法。Watkins提出了Q学习的基本算法，尽管他证明了在满足一定条件下Q值学习的迭代公式的收敛性，但是在他给出的算法中，没有考虑到在迭代过程中初始状态与初始动作的选取对后继学习的影响，因此提出的关联值递归Q学习算法改进了原来的Q学习算法，并且这种算法有比较好的收敛性质，从求解最优费用函数的方法出发，给出了Q学习的关联值递归算法，这种方法的建立可以使得动态规划（DP）算法中的许多结论直接应用到Q学习的研究中来。     

Q-Learning: computation of optimal Q-values for evaluating the learning level in robotic tasks

A problem related to the use of reinforcement learning (RL) algorithms on real robot applications is the difficulty of measuring the learning level reached after some experience. Among the different RL algorithms, the Q-learning is the most widely used in accomplishing robotic tasks. The aim of this work is to a priori evaluate the optimal Q-values for problems where it is possible to compute the distance between the current state and the goal state of the system. Starting from the Q-learning updating formula the equations for the maximum Q-weights, for optimal and non-optimal actions, have been computed considering delayed and immediate rewards. Deterministic and non deterministic grid-world environments have been also considered to test in simulations the obtained equations. Besides the convergence rates of the Q-learning algorithm have been compared using different learning rate parameters.     

一种新的多智能体Q学习算法

针对非确定马尔可夫环境下的多智能体系统,提出了一种新的多智能体Q学习算法.算法中通过对联合动作的统计来学习其它智能体的行为策略,并利用智能体策略向量的全概率分布保证了对联合最优动作的选择. 同时对算法的收敛性和学习性能进行了分析.该算法在多智能体系统RoboCup中的应用进一步表明了算法的有效性与泛化能力.     

Backward Q-learning: The combination of Sarsa algorithm and Q-learning

Reinforcement learning (RL) has been applied to many fields and applications, but there are still some dilemmas between exploration and exploitation strategy for action selection policy. The well-known areas of reinforcement learning are the Q-learning and the Sarsa algorithms, but they possess different characteristics. Generally speaking, the Sarsa algorithm has faster convergence characteristics, while the Q-learning algorithm has a better final performance. However, Sarsa algorithm is easily stuck in the local minimum and Q-learning needs longer time to learn. Most literatures investigated the action selection policy. Instead of studying an action selection strategy, this paper focuses on how to combine Q-learning with the Sarsa algorithm, and presents a new method, called backward Q-learning, which can be implemented in the Sarsa algorithm and Q-learning. The backward Q-learning algorithm directly tunes the Q-values, and then the Q-values will indirectly affect the action selection policy. Therefore, the proposed RL algorithms can enhance learning speed and improve final performance. Finally, three experimental results including cliff walk, mountain car, and cart–pole balancing control system are utilized to verify the feasibility and effectiveness of the proposed scheme. All the simulations illustrate that the backward Q-learning based RL algorithm outperforms the well-known Q-learning and the Sarsa algorithm.     

基于强化学习的城市交通路径规划

城市交通路径规划需要考虑规划的快速性和车辆的安全性,而目前大多数强化学习算法不能兼顾两者.针对这个问题,首先提出采用基于模型的算法和与模型无关的算法相结合的Dyna框架,以提高规划的速度;然后使用经典的Sarsa算法作为选路策略,以提高算法的安全性;最后将两者结合提出了改进的基于Sarsa的Dyna-Sa算法.实验结果...     

改进强化学习算法的UAV室内三维航迹规划

随着室内导航定位技术的兴起,无人机（Unmanned Aerial Vehicle,UAV）技术在室内环境中的应用得到前所未有的发展,对无人机航迹规划能力提出了更高的要求。由于室内环境空间较为复杂,且现有的强化学习算法收敛速度慢,提出一种基于强化学习的集成方法。通过给定的起点和终点位置的坐标连线,判断出主要障碍物及围绕主要障碍物的节点,减少无用节点的搜索;在Q值初始化过程中通过数学关系构造出方向趋向函数,确定出目标点所在的方向,以提高算法的收敛速度;在三维栅格地图中对优化算法进行仿真验证。仿真结果表明：改进的三维航迹规划算法使得空间搜索节点数目减少了55.49%,收敛时间缩短了98.57%。     

基于每阶段平均费用最优的激励学习算法

文中利用求解最优费用函数的方法给出了一种新的激励学习算法，即基于每阶段平均费用最优的激励学习算法。这种学习算法是求解信息不完全Markov决策问题的一种有效激励学习方法，它从求解分阶段最优平均费用函数的方法出发，分析了最优解的存在性，分阶段最优平均费用函数与初始状态的关系以及与之相关的Bellman方程。这种方法的建立，可以使得动态规划（DP）算法中的许多结论直接应用到激励学习的研究中来。     

融合认知行为模型的深度强化学习框架及算法

面对高维连续状态空间或稀疏奖励等复杂任务时,仅依靠深度强化学习算法从零学习最优策略十分困难,如何将已有知识表示为人与学习型智能体之间相互可理解的形式,并有效地加速策略收敛仍是一个难题.对此,提出一种融合认知行为模型的深度强化学习框架,将领域内先验知识建模为基于信念-愿望-意图(belief- desire-intention, BDI)的认知行为模型,用于引导智能体策略学习.基于此框架,分别提出融合认知行为模型的深度Q学习算法和近端策略优化算法,并定量化设计认知行为模型对智能体策略更新的引导方式.最后,通过典型gym环境和空战机动决策对抗环境,验证所提出算法可以高效利用认知行为模型加速策略学习,有效缓解状态空间巨大和环境奖励稀疏的影响.     

基于有限样本的最优费用关联值递归Q学习算法

一个激励学习Agent通过学习一个从状态到动作映射的最优策略来求解决策问题。求解最优决策一般有两种途径,一种是求最大奖赏方法,另一种是求最优费用方法。该文利用求解最优费用函数的方法给出了一种新的Q学习算法。Q学习算法是求解信息不完全Markov决策问题的一种有效激励学习方法。文章从求解最优费用函数的方法出发,给出了Q学习的关联值递归算法,这种方法的建立,可以使得动态规划(DP)算法中的许多结论直接应用到Q学习的研究中来。     

Learning classifier systems from a reinforcement learning perspective

 We analyze learning classifier systems in the light of tabular reinforcement learning. We note that although genetic algorithms are the most distinctive feature of learning classifier systems, it is not clear whether genetic algorithms are important to learning classifiers systems. In fact, there are models which are strongly based on evolutionary computation (e.g., Wilson's XCS) and others which do not exploit evolutionary computation at all (e.g., Stolzmann's ACS). To find some clarifications, we try to develop learning classifier systems “from scratch”, i.e., starting from one of the most known reinforcement learning technique, Q-learning. We first consider thebasics of reinforcement learning: a problem modeled as a Markov decision process and tabular Q-learning. We introduce a formal framework to define a general purpose rule-based representation which we use to implement tabular Q-learning. We formally define generalization within rules and discuss the possible approaches to extend our rule-based Q-learning with generalization capabilities. We suggest that genetic algorithms are probably the most general approach for adding generalization although they might be not the only solution.     

基于概率模型的动态分层强化学习

为解决大规模强化学习中的＂维度灾难＂问题,克服以往学习算法的性能高度依赖于先验知识的局限性,本文提出一种基于概率模型的动态分层强化学习方法.首先基于贝叶斯学习对状态转移概率进行建模,建立基于概率参数的关键状态识别方法,进而通过聚类动态生成若干状态子空间和学习分层结构下的最优策略.仿真结果表明该算法能显著提高复杂环境下智能体的学习效率,适用于未知环境中的大规模学习.     

基于动态规划方法的激励学习遗忘算法

一个激励学习Agent通过学习一个从状态到动作映射的最优策略来解决策问题。激励学习方法是Agent利用试验与环境交互以改进自身的行为。Markov决策过程(MDP)模型是解决激励学习问题的通用方法,而动态规划方法是Agent在具有Markov环境下与策略相关的值函数学习算法。但由于Agent在学习的过程中,需要记忆全部的值函数,这个记忆容量随着状态空间的增加会变得非常巨大。文章提出了一种基于动态规划方法的激励学习遗忘算法,这个算法是通过将记忆心理学中有关遗忘的基本原理引入到值函数的激励学习中,导出了一类用动态规划方法解决激励学习问题的比较好的方法,即Forget-DP算法。     

基于强化学习的交通情景问题决策优化

在复杂交通情景中求解出租车路径规划决策问题和交通信号灯控制问题时,传统强化学习算法在收敛速度和求解精度上存在局限性;因此提出一种改进的强化学习算法求解该类问题。首先,通过优化的贝尔曼公式和快速Q学习（SQL）机制,以及引入经验池技术和直接策略,提出一种改进的强化学习算法GSQL-DSEP;然后,利用GSQL-DSEP算法分别优化出租车路径规划决策问题中的路径长度与交通信号灯控制问题中的车辆总等待时间。相较于Q学习、快速Q学习（SQL）、、广义快速Q学习（GSQL）、Dyna-Q算法,GSQL-DSEP算法在性能测试中降低了至少18.7%的误差,在出租车路径规划决策问题中使决策路径长度至少缩短了17.4%,在交通信号灯控制问题中使车辆总等待时间最多减少了51.5%。实验结果表明,相较于对比算法,GSQL-DSEP算法对解决交通情景问题更具优势。     

基于Q—learning的一种多Agent系统结构模型

多Agent系统是近年来比较热门的一个研究领域,而Q-learning算法是强化学习算法中比较著名的算法,也是应用最广泛的一种强化学习算法。以单Agent强化学习Qlearning算法为基础,提出了一种新的学习协作算法,并根据此算法提出了一种新的多Agent系统体系结构模型,该结构的最大特点是提出了知识共享机制、团队结构思想和引入了服务商概念,最后通过仿真实验说明了该结构体系的优越性。