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Walk this way: To be useful around people, robots need to learn how to move like we do
Abstract
Robots have walked on legs for decades. Today's most advanced humanoid robots can tramp along flat and inclined surfaces, climb up and down stairs, and slog through rough terrain. Some can even jump. But despite the progress, legged robots still can't begin to match the agility, efficiency, and robustness of humans and animals. • Existing walking robots hog power and spend too much time in the shop. All too often, they fail, they fall, and they break. For the robotic helpers we've long dreamed of to become a reality, these machines will have to learn to walk as we do. • We must build robots with legs because our world is designed for legs. We step through narrow spaces, we navigate around obstacles, we go up and down steps. Robots on wheels or tracks can't easily move around the spaces we've optimized for our own bodies.
... In addition, the desired touch-down and lift-off times d t( d v x ) = [ d t TD d t LO ] T are determined from data of human running acquired in another study, provided the desired horizontal velocity d v x . The actual touch-down and lift-off times can be calculated from Equations (94) and (96) as [t TD t LO ] T = g S (x Sn , u Sn ). Then, an optimization problem to synthesize a running gait trajectory can be represented as ...
... It performed robust walking on uneven terrain without any external sensors and fast running at 2.5 m/s with high energy efficiency quantified by 1.3 total cost of transport (TCoT) [95]. Two biped robots Cassie and Digit developed by Agility Robotics inherited the design concept of ATRIAS [96]. ...
Studies of biped control including standing, walking, hopping and running on humanoid robots are reviewed in this survey paper. Model-based approaches standing upon reduced-order dynamics are focused. It begins with revisiting the centroidal dynamics and the zero-moment point, which leads to the linear inverted pendulum (LIP) model and some of its variations. Then, some representative standing and walking control techniques based on the LIP model are reviewed, where the concept of capturability is also discussed. It is followed by consideration of height variation of the center of mass. Enhancement to hopping and running motions, which include aerial phases, is also addressed. Ideas to deal with complex nature as a hybrid system underlying discontinuously varying mechanics mainly due to unilateral constraints on contact forces are concisely explained.
... Legged robotic platforms have gained widespread accessibility and are often envisioned as versatile mobile platforms suitable for navigating challenging and unstructured environments. Consequently, most robotic systems are engineered and controlled with utility and efficiency as the primary objectives [15]. This has led to remarkable achievements in dynamic legged systems that can now hike up mountains [28] and conquer obstacle courses [13]. ...
Legged robots have achieved impressive feats in dynamic locomotion in challenging unstructured terrain. However, in entertainment applications, the design and control of these robots face additional challenges in appealing to human audiences. This work aims to unify expressive, artist-directed motions and robust dynamic mobility for legged robots. To this end, we introduce a new bipedal robot, designed with a focus on character-driven mechanical features. We present a reinforcement learning-based control architecture to robustly execute artistic motions conditioned on command signals. During runtime, these command signals are generated by an animation engine which composes and blends between multiple animation sources. Finally, an intuitive operator interface enables real-time show performances with the robot. The complete system results in a believable robotic character, and paves the way for enhanced human-robot engagement in various contexts, in entertainment robotics and beyond.
... Legged robotic platforms have gained widespread accessibility and are often envisioned as versatile mobile platforms suitable for navigating challenging and unstructured environments. Consequently, most robotic systems are engineered and controlled with utility and efficiency as the primary objectives [15]. This has led to remarkable achievements in dynamic legged systems that can now hike up mountains [28] and conquer obstacle courses [13]. ...
... The passivedynamic walker designed by Steve et al. was able to walk down a slope stably without any other energy input [18], but its speed and versatility are limited due to total passive actuation. Compared to a human body, whose CoT is 0.2, conventional humanoid robots have much higher CoT values ranging between 2 and 3. ATRIAS, the previous version of Cassie [19], one of the most efficient legged robot, has a CoT of 1.13 [20]. Unitree B2, a quadruped robot product, can travel 20 km in 5 hours, whose CoT reaches 0.68. ...
This letter proposes a novel mechanical structure for traditional articulated-legged robots that uses a linkage-based approach and hydrostatic transmission to reduce the joint load caused by gravity. The wide application of legged robots is limited by their weight-bearing capacity and low energy efficiency. To address these issues, we built HyELeg2, a motor-actuated bipedal robot with the assistance of a hydraulic auxiliary mechanism. HyELeg2 employs one passive hydraulic cylinder per leg to counterbalance the joint torque induced by the body mass at both knee and hip joints. During the stance phase of walking, the cylinder can provide upward support force passively to reduce the energy cost of motors. To control the flow efficiently, a rotary-cage valve (RCV) was developed with low energy consumption and low flow resistance. Contrast experiments were conducted to investigate the energy-saving effects of HyELeg2 under different speed, gait frequency and load conditions. The results indicate that hydraulic assistance saves energy by more than 65% to perform the same walking tasks, and greatly reduces the cost of transport (CoT). This study has high practical value in the legged robot field.
... After the DRC, novel humanoid platforms have been developed following different design paradigms, in particular: relocating actuators to improve mass distribution, especially on the legs, and employing different actuation units than classical electrical actuators with harmonic drivers, to enhance impact robustness and torque/force control. Remarkable examples of this new generation of biped robots are the new Atlas from Boston Dynamics, see [13], Cassie/Digit from Agility Robotics [14], and UCLA's Artemis [15]. While Atlas relies on hydraulic actu-ation to achieve robustness and high-power impulsive motions, Cassie/Digit and Artemis use high-torque motors paired with high-efficiency low-reduction-ratio gearboxes located near the main body of the robot, with the motion transmitted through a series of closed linkages to reduce foot inertia. ...
This paper presents the modeling and numerical analysis of the Kangaroo lower body prototype, a novel bipedal humanoid robot developed and manufactured by PAL Robotics. Kangaroo features high-power linear electric actuators combined with unique serial-parallel hybrid chains, which allow for the positioning of all the leg actuators near the base of the robot in order to improve the overall mass distribution. To model and analyze such complex nonlinear mechanisms, we employ a constrained formulation that is extended to account for floating-base systems in contact with the environment. A comparison is made to demonstrate the significant improvements achieved with TALOS, another humanoid bipedal robot designed by PAL Robotics, in terms of equivalent Cartesian inertia at the feet and centroidal angular momentum. Finally, the paper includes numerical experiments conducted through simulation and preliminary tests performed on the actual Kangaroo platform.
... From the control perspective, these robots are high-dimensional and non-smooth systems with many physical constraints [11]. In practice, these restrictions lead to substantial compromises in performance, such as slow acceleration [12], a fixed upright pose of the body, and limited velocity of the limbs [13]. The contact points change over time depending on the maneuver being performed and, therefore, cannot be prespecified [14]. ...
Introducing Myrmex, a hexapod robot designed for autonomous locomotion on unstructured terrains. It was developed a whole-body kinematics model that enables both open-chain and closed-chain control of the robot. This model enhances the flexibility and mobility of the robot. At the moment, Myrmex relies solely on proprioception (encoders and IMU) for adapting its body posture. Despite these sensory limitations, we have successfully applied the model in static and dynamic situations. Static experiments have showcased increased flexibility, allowing the robot to access previously challenging locations. In dynamic scenarios, the hexapod has demonstrated its capability to traverse irregular terrains, effectively exploiting its body mobility. Myrmex adeptly adjusts its posture according to the terrain topology, maintaining the center of gravity projection along the body’s centerline (i.e., same as it in the level walk), thus preserving stability margins during gait. The robot was able to correct its posture on terrain with gradients in any direction relative to the body structure, with only 3 DoF per leg. Importantly, our experiments have underscored the robot’s ability to maintain its posture even in the face of unexpected disturbances in its legs, emphasizing the robustness and reliability of the model.
... There were products with direct-drive actuation in the 1980s but perhaps the first harbingers of substantial commercial application are now appearing, first in specialized applications [1], and subsequently in general purpose manipulators [15,14]. As motor technology has improved, the well-known advantages of direct-drive (and low gear ratios more generally) has led to a greater interest in the locomotion community [13,42,19,24,22]. In particular, [24] contains an overview of the advantages and disadvantages of direct-drive, applied to locomotion. ...
... This bipedal robot is developed by agility robotics which is the descendant of another robot of agility robotics, Cassie. DIGIT has some updated sensors, including a LiDAR atop the torse, which helps to navigate an environment full of obstacles and helps to navigate on stairs (Hurst, 2019). ...
Researchers around the world are developing autonomous robot systems to assist humans with tedious, hazardous, complex, and time-consuming tasks. Today, autonomous robots are used for a variety of applications, ranging from delivering food to operating on patients. A robotic system can be operated with or without human assistance, depending on whether it is manned or unmanned. Additionally, the robot may be classified as an Unmanned Aerial Vehicle (UAV), Unmanned Surface Vehicle (USV), or Unmanned Ground Vehicle (UGV), depending on its operational conditions. An autonomous robot may be equipped with manipulators and advanced sensors, such as a LiDAR camera, which can collect 3D spatial data. The present study reviews recent research and development of unmanned ground vehicles, including two nature-inspired designed robots called SPOT and DIGIT and presents its technical data. In addition, this study introduces the challenges and applications of these robots. A novel type of comparison was made in this study between some UGVs, human and animal-inspired designed robots, where researchers were able to get an idea of different robot basic specifications that could be used to select these robots for future research. As a result of this study, two more studies will be conducted in the future.
... Among the different factors involved in HRI, perhaps the least mediatic, but no less important is related to the humanoid movement of robots [5]. This movement is perceived unconsciously by humans and is not limited just to the robot's arms, but also extends to other movements such as those of the robot's head, eye blinking, mouth movement, hands, etc. [6,7]. ...
Collaborative robots or cobots interact with humans in a common work environment.
In cobots, one under-investigated but important issue is related to their movement and how it is perceived by humans. This paper tries to analyze whether humans prefer a robot moving in a human or in a robotic fashion. To this end, the present work lays out what differentiates the movement performed by an industrial robotic arm from that performed by a human one. The main difference lies in the fact that the robotic movement has a trapezoidal speed profile, while for the human arm, the speed profile is bell-shaped and during complex movements, it can be considered as a sum of superimposed bell-shaped movements. Based on the lognormality principle, a procedure was developed for a robotic arm to perform human-like movements. Both speed profiles were implemented in two industrial robots, namely, an ABB IRB 120 and a Universal Robot UR3. Three tests were used to study the subjects’ preference when seeing both movements and another analyzed the same when interacting with the robot by touching its ends with their fingers.
... Some modern bipedal and humanoid robots that achieved fast walking overcame these shortcomings by utilizing human-like walking involving toe-off, heelstrike, and knee stretching [1,2]. One exception would be the bipedal robot Cassie [3], which recently achieved 5 km/h walking with bird-like leg design. In this case, however, high cadence (roughly 0.3 s per step) largely contributed to high walking speed, which requires a lightweight leg design. ...
A planning algorithm that can generate continuous-time walking patterns including the seamless transition between flat-contact and heel-to-toe walking gaits is proposed. The planner makes use of the closed-form solution of a modified linear inverted pendulum mode which includes the ZMP and the weight ratio of each foot explicitly in its dynamics. The heel-to-toe movement of each foot is directly parameterized by the ZMP, and therefore consistency between the foot movement and the low-dimensional dynamics is ensured. In simulations with a 32 DoF model of a life-sized humanoid robot, fast human-like walking at the maximum speed of 4.6 km/h was achieved.
... Basically, actuators are responsible for moving the passive parts of the robots such as links, in a coordinated manner. Electric motors (EM) or Hydraulic actuators (HA) are widely utilized in legged robots (e.g., EM in Asimo (Sakagami et al. 2002), Cassie (Hurst et al. 2019), Spot robot series and HRP-4 or HA in ATLAS, PetMan (Nelson et al. 2012), BigDog (Raibert et al. 2008) or HyQ (Semini et al. 2011). Although with these actuators either position or torque control is achievable with high precision, there are issues hindering them from being perfect actuators for locomotion. ...
Compared to biological muscles, current technical actuators are limited in their performance and versatility to realize human-like locomotion. In order to overcome the actuator limitations for locomotion, we introduce the hybrid EPA actuator as a combination of electric and pneumatic actuators in this chapter. As a new variable impedance actuator, the EPA design provides direct access to the control and morphological properties. We demonstrate that with the EPA, the actuator limitations could be clearly reduced in vertical hopping.
... Unlike conventional robot systems, the position of the robot is determined by the IR sensor and color sensor. The robotic arm can be directed to select and displace any object which position is known in the working space [4,5]. ...
Control of the robot is an important place for the use of robot technology. The use of robots is continually extending. Today, the usage of robots is at most 5% all over the world in the industry. According to The International Federation of Robotics (IFR) data, this usage rate is estimated to be more than 2 million in the world between 2018 and 2021. One of the applications is the usage of robotic technology such as office environment, military duties, hospital operations, etc. Moreover, robots are rather invaluable in complicated or hazardous processes like toxic materials, neutralizing explosives, or performing certain specific repetitive tasks in industries, instead of human interference. Sensors play a significant role in performing the functions of robots in all these processes. There was mentioned the importance of using open-source robot arms with professional features and industrial scale in terms of decreasing workload of hospital staff. Today, the priority is human health, and how significant any system developed in the health system is more understood especially in the pandemic process. For this reason, the open-source robot arm is analyzed and it will not be an issue such as copyright, it can be printed from 3D printers and it saves more budget. Additionally, robot arm kinematic analysis was done to define the workspace.
... Unlike conventional robot systems, the position of the robot is determined by the IR sensor and color sensor. The robotic arm can be directed to select and displace any object which position is known in the working space [4,5]. ...
Today, it is especially estimated that robots will be more than 2 million between 2018-2021, with their increasing use in the industry, in the world. In the industrial environment, robots are used to neutralize toxic substances, explosives, or to replace certain repetitive tasks in the industry for human intervention. On the other hand, robotic systems are used in different areas such as office environment, military duties, and use in hospital environments. It is widespread the use of open-source design robot day by day, in addition to the increasing use of robots, which have invaluable effective uses in complex or dangerous processes. The use of open-source robotic systems is cheaper, developable, and has no usage restrictions due to copyright compared to equivalent robots used in the industry. For these reasons, in our study, a robotic arm with 5 degrees of freedom, printed with 3D printers at industrial scales, was developed. The printed robotic arm was developed to be used as an auxiliary equipment for hospital staff, especially in today's hospital environment. Kinematic analysis is required to determine the working space of the developed robotic arm. The working space of the robotic arm, which is intended to be used as auxiliary equipment in the hospital environment, was revealed by kinematic analysis.
... The hydraulically-actuated quadruped (HyQ) robot [4] [5] and the Boston Dynamics' SpotMini also have manipulation capabilities. For humanoid robots such as Digit [6], Toro [7], and Boston Dynamic's Atlas, arms are an inherent part of their humanoid physiology. ...
Manipulators can be added to legged robots, allowing them to interact with and change their environment. Legged mobile manipulation planners must consider how contact forces generated by these manipulators affect the system. Current planning strategies either treat these forces as immutable during planning or are unable to optimize over these contact forces while operating in real-time. This paper presents the Stability and Task Oriented Receding-Horizon Motion and Manipulation Autonomous Planner (STORMMAP) that is able to generate continuous plans for the robot's motion and manipulation force trajectories that ensure dynamic feasibility and stability of the platform, and incentivizes accomplishing manipulation and motion tasks specified by a user. STORMMAP uses a nonlinear optimization problem to compute these plans and is able to run in real-time by assuming contact locations are given a-priori, either by a user or an external algorithm. A variety of simulated experiments on a quadruped with a manipulator mounted to its torso demonstrate the versatility of STORMMAP. In contrast to existing state of the art methods, the approach described in this paper generates continuous plans in under ten milliseconds, an order of magnitude faster than previous strategies.
... The history of humanoid robot locomotion began with conservative gait where the ZMP or the ground projection of the COM is kept close to the centroid of the BOS [35]. With the adoption of new criteria, advanced platforms and controllers for dynamic gait have been developed where the ground projection of the COM is no longer restricted to the BOS [34,[36][37][38][39][40][41][42]. ...
To achieve walking and push recovery successfully, a biped robot must be able to determine if it can maintain its current contact configuration or transition into another one without falling. In this work, the ability of a biped robot to maintain single support (SS) or double support (DS) contact and to achieve a step are represented by balanced and steppable regions, respectively, as proposed partitions of an augmented center-of-mass-state space. These regions are constructed with an optimization method that incorporates full system dynamics, system properties such as kinematic and actuation limits, and contact interactions with the environment in two-dimensional sagittal plane. The SS balanced, DS balanced, and steppable regions are obtained for both experimental and simulated walking trajectories of the robot with and without the swing foot velocity constraint to evaluate the contribution of the swing leg momentum. A comparative analysis against 1-step capturability, the ability of a biped to come to a stop after a step, demonstrates that the computed steppable region significantly exceeds the 1-step capturability of an equivalent reduced-order model. The use of balanced regions to characterize the full balance capability criteria of the system and benchmark controllers are demonstrated with three push recovery controllers. The implemented hip-knee-ankle controller resulted in improved stabilization with respect to decreased foot tipping and time required to balance, relative to an existing hip-ankle controller and a gyro balance feedback controller.
... The spring loaded inverted pendulum (SLIP) model is particularly applicable for agile locomotion because it demonstrates strong stabilizing effects [4], [5] and reproduces the dynamics of human walking, human running, and guinea fowl running [6], [7]. Many agile robots closely resemble the SLIP model [8], [9] or are designed with SLIP locomotion as a goal [10], [11], which motivates our choice to use an actuated variation of the SLIP model in this letter. In this paper we present a method of using reducedorder models of walking to direct high quality, transferable walking controllers and demonstrate its effectiveness on a Cassie series robot from Agility Robotics. ...
In this paper, we describe an approach to achieve dynamic legged locomotion on physical robots which combines existing methods for control with reinforcement learning. Specifically, our goal is a control hierarchy in which highest-level behaviors are planned through reduced-order models, which describe the fundamental physics of legged locomotion, and lower level controllers utilize a learned policy that can bridge the gap between the idealized, simple model and the complex, full order robot. The high-level planner can use a model of the environment and be task specific, while the low-level learned controller can execute a wide range of motions so that it applies to many different tasks. In this letter we describe this learned dynamic walking controller and show that a range of walking motions from reduced-order models can be used as the command and primary training signal for learned policies. The resulting policies do not attempt to naively track the motion (as a traditional trajectory tracking controller would) but instead balance immediate motion tracking with long term stability. The resulting controller is demonstrated on a human scale, unconstrained, untethered bipedal robot at speeds up to 1.2 m/s. This letter builds the foundation of a generic, dynamic learned walking controller that can be applied to many different tasks.
... To meet the above requirements, a humanoid robot is the first option. Digit from Agility Robotics [16], Atlas from Boston Dynamics, and Asimo from Honda are all humanoid robots with excellent performance [17], but the biggest problem is the high complexity of their structure and control system, which also means high costs. Although some scholars proposed a more simplified humanoid robot structure and control strategy [18], the simplified mechanical structure increases the area of its feet, almost occupying the platform of an entire stair during stair-climbing, which impacts people passing on the stairs. ...
The rapid development of e-commerce makes the last-mile problem more and more prominent. To meet the requirements of such a scenario, this paper proposes a robot with a decoupled mechanical structure. Such a hexapod robot is divided into a chassis frame with a pair of auxiliary wheel-legs for horizontal movement, a tetrapod for vertical movement, and a slide-and-rail mechanism to connect the former two parts. Such a structure is simple and, thus, cost-efficient; by managing the horizontal and vertical movements, such a robot can keep the balance and safety of the load in the various operation environments, such as roads, staircases, and even indoor ones. Meanwhile, a state-machine-based controller, which adapts well to the unique structure of the proposed robot, is also proposed, simplifying the sequential control of the robot. A prototype robot with 30-kg load ability was built, and the experimental results prove the validity of the design.
... At the balanced extreme of this spectrum, the robot is overly balanced and employs conservative (and thus energetically inefficient) walking during the entire gait cycle with bent knees and small step length relative to its foot dimension. These characteristics are typical in most (but not all [62,63,64,65,66]) current humanoid robots. The robot's Fig. 7. Non-dimensionalized comparison of gait stability for COM state trajectories of the robot, human, and rimless and circular wheels with respect to their balanced and steppable regions. ...
In this work, the role of swing limb dynamics in the stabilization of legged systems is investigated. To quantify the contribution of arm swing during whole-body balancing, the balancing capability of a bipedal robotic platform is evaluated computationally during single and double foot contact for two configurations: arms fixed and arms free to move. The balancing capability with each arm configuration is evaluated by constructing its corresponding balance stability boundary, a threshold between balanced and falling states that includes all possible center of mass (COM) states that are balanced with respect to the specified arm and foot contact configuration. In this analysis, the bipedal robotic platform is modeled as a kinematic tree structure with floating-base dynamics in the sagittal plane. In addition to floating-base and joint-space dynamics, the complete COM-space dynamics of the system is established, including the formulation of the angular momentum (and its rate) of each rigid link, as well as a model of actuation dynamics based on motor characteristics. The comparison of the two balance stability regions yields both a quantitative measure of the enhancement in total balance capability and qualitative insights into the mechanism by which arm swing leads to enhanced capability. The role of arm swing angular momentum is also analyzed from the robot’s experimental gait trajectories as a potential means of benchmarking controller performance.
... Potentially, we would like to transfer this gained knowledge to controller and robot design. A similar approach was used for designing the robots ATRIAS and Cassie, which utilize a birdinspired SLIP concept to achieve efficient and dynamic gaits [25,26]. But, even these studies often maintain the trunk posture at a fixed angle without any movements. ...
Bipedal animals have diverse morphologies and advanced locomotion abilities. Terrestrial birds in particular, display agile, efficient, and robust running motion, in which they exploit the interplay between the body segment masses and moment of inertias. On the other hand, most legged robots are not able to generate such versatile and energy efficient motion and often disregard trunk movements as a means to enhance their locomotion capabilities. Recent research investigated how trunk motions affect the gait characteristics of humans, but there is a lack of analysis across different bipedal morphologies. To address this issue, we analyze avian running based on a spring-loaded inverted pendulum model with a pronograde (horizontal) trunk. We use a virtual point based control scheme and modify the alignment of the ground reaction forces to assess how our control strategy influences the trunk pitch oscillations and energetics of the locomotion. We derive three potential key strategies to leverage trunk pitch motions that minimize either the energy fluctuations of the center of mass or the work performed by the hip and leg. We show that these strategies are also valid for human-like trunks, and could be used in legged robotics.
... Neatless integration of robots is a major enabler of next generation industrial production lines, and will as well play an important role in the society of the future. Especially legged robots are of importance since they can provide a flexibility in movement comparable to the human one [1]. ...
Behaviors of animal bipedal locomotion can be described, in a simplified form, by the bipedal spring-mass model. The model provides predictive power, and helps us understand this complex dynamical behavior.
In this paper, we analyzed a range of gaits generated by the bipedal spring-mass model during walking, and proposed a stabilizing touch-down condition for the swing leg. This policy is stabilizing against disturbances inside and outside the same energy level and requires only internal state information. In order to generalize the results to be independent of size and dimension of the system, we nondimensionalized the equations of motion for the bipedal spring-mass model. We presented the equilibrium gaits (a.k.a fixed point gaits) as a continuum on the walking state space showing how the different types of these gaits evolve and where they are located in the state space. Then, we showed the stability analysis of the proposed touch-down control policy for different energy levels and leg stiffness values. The results showed that the proposed touch-down control policy can stabilize towards all types of the symmetric equilibrium gaits. Moreover, we presented how the peak leg force change within an energy level and as it changes due to the type of the gait; peak force is important as a measurement of injury or damage risk on a robot or animal. Finally, we presented simulations of the bipedal spring-mass model walking on level ground and rough terrain transitioning between different equilibrium gaits as the energy level of the system changes with respect to the ground height. The analysis in this paper is theoretical, and thus applicable to further our understanding of animal bipedal locomotion and the design and control of robotic systems like ATRIAS, Cassie, and Digit.
Collaborative robots or cobots interact with humans in a common work environment. In cobots, one under investigated but important issue is related to their movement and how it is perceived by humans. This paper tries to analyze whether humans prefer a robot moving in a human or in a robotic fashion. To this end, the present work lays out what differentiates the movement performed by an industrial robotic arm from that performed by a human one. The main difference lies in the fact that the robotic movement has a trapezoidal speed profile, while for the human arm, the speed profile is bell-shaped and during complex movements, it can be considered as a sum of superimposed bell-shaped movements. Based on the lognormality principle, a procedure was developed for a robotic arm to perform human-like movements. Both speed profiles were implemented in two industrial robots, namely, an ABB IRB 120 and a Universal Robot UR3. Three tests were used to study the subjects' preference when seeing both movements and another analyzed the same when interacting with the robot by touching its ends with their fingers.
Animals are much better at running than robots. The difference in performance arises in the important dimensions of agility, range, and robustness. To understand the underlying causes for this performance gap, we compare natural and artificial technologies in the five subsystems critical for running: power, frame, actuation, sensing, and control. With few exceptions, engineering technologies meet or exceed the performance of their biological counterparts. We conclude that biology’s advantage over engineering arises from better integration of subsystems, and we identify four fundamental obstacles that roboticists must overcome. Toward this goal, we highlight promising research directions that have outsized potential to help future running robots achieve animal-level performance.
In this paper, we review monolithic and reconfigurable modular robotic systems, focusing on configuration detection and legged locomotion. The focus of the review lies on the realization of a robotic system consisting of autonomous robotic legs with integrated PC and power units and grants a specialized look at embodiment for such robots. We further dissect the challenges of disembodied modular legged systems and propose how they may be realized using configuration detection. This is necessary in case the configuration as well as the payload is unknown to the robot. Using the state of the art approaches, we propose a approach for the realization of a modular disembodied legged robot consisting of a list of methods focussing on individual issues in the realization of such autonomous legs. We close with an outlook on future challenges for such a system and what research fields will need to be exploited.
A unified framework is established for general balance stability criteria of biped systems. The stability regions of balanced and steppable states are partitions of the center-of-mass (COM) state space that is augmented for general biped systems and tasks. Their boundaries are the set of maximum allowable COM velocity perturbations, under which a specified contact can be maintained (balanced) or a desired step can be made (steppable). Whole-body models with full-order dynamics and system-specific kinematic and actuation limits are established to quantify the effects of momenta and stepping on the system's balance stability under contact interactions. The generality of the framework with respect to systems and tasks is verified with a humanoid robot and a human for walking and standing. Validity and implications of the computed stability regions are demonstrated in the sagittal plane through comparative analyses across strategies and against existing criteria (capturability and zero-moment point), reduced-order models, and simulations. Distinct stability characteristics of experimental walking for the robot (overly balanced) versus humans (unbalanced but steppable) are validated, and the walking principle is analyzed. The partitions also provide inter/intra-region analyses of multi-level momentum and stepping strategies for balancing. A partition-aware controller is implemented for the robot to monitor the stability of the current state and selectively exploit stabilizing actions during simulated standing push recovery.
In this chapter, the basic mechanical setup is described and its potential for human-machine interaction and how it can be leveraged by design and hardware integration is discussed.
The application of hybrid mechanisms in the field of humanoid robots has attracted significant attention. A novel eight-degree-of-freedom hybrid manipulator is proposed to realize a kinematic function similar to that of the human arm. A general method for solving the inverse displacement problem of hybrid mechanisms is given, and the proposed humanoid robotic arm is taken as an example to demonstrate the solution process of this method. Furthermore, a closed-form solution for the inverse displacement problem of the hybrid humanoid robotic arm is derived by using the given method based on screw theory, exponential product formula, and Paden–Kahan subproblems. In addition, the problem of verifying and selecting the appropriate solutions according to the starting postures is also illustrated in a series of simulation experiments. Simulation experiment results show that there are (at most) 32 sets of solutions for the proposed humanoid robotic arm according to the same target position-orientation matrix and the given redundant input variables, and the accuracy of the proposed method for solving the inverse displacement problem is verified.
In this paper, the contour of aero-engine blade is fitted with spline curve, and the surface of the blade is segmented according to the fitted curve curvature. The mathematical model of continuous precession of blade surface grinding is established, and the algorithm of grinding path is studied. A program capable of simulating the surface grinding path of the blade was developed. 3-D reconstruction of the blade using the blade contour fitting curve was established. The experiments in this paper were performed on a system consisting of two robots, one of which was responsible for the blade space adjustment for its partition segment, and another robot responsible for the path of the grinding. This paper presents the experimental results data, analyzes the data, and selects some experimental condition parameters that can obtain better results.
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