Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center

Fengcheng, China

Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center

Fengcheng, China
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Wang R.,Northwestern Polytechnical University | Zhao W.,Northwestern Polytechnical University | Zhao W.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Li S.,Northwestern Polytechnical University | Zhang S.,Northwestern Polytechnical University
2016 IEEE International Conference on Robotics and Biomimetics, ROBIO 2016 | Year: 2016

Payload capacity of running robots with compliant legs is a very important subject for robotic researchers, with the fact that SLIP model, two-segment leg model with constant spring stiffness and with 'J'-curve spring stiffness are regarded as an effective tool as well as a good basis for the study of running robots with compliant legs. However, in fast locomotion, little work has been done on the relationship between leg compliance and payload capacity based on these three models. Thus, at high speed we adopt the steps-to-fall method and the apex return map to investigate the influence of leg stiffness on payload capacity in all three models. Simulation results reveal that in all three models the two-segment leg model with J-curve spring stiffness shows the largest stability region, and for the same payloads the tolerated minimum reference stiffness is the lowest. In other words, for the same leg stiffness, it provides the maximum payload capacity in all three models. Thus, at high speed two-segment leg model with 'J'-curve spring stiffness is more propitious for high-payload running compared with the other two models. © 2016 IEEE.


Qin X.,Northwestern Polytechnical University | Qin X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.,Northwestern Polytechnical University | Tan X.,Northwestern Polytechnical University | And 2 more authors.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2013

For discrete ground contact, there were high adaptability and extensive application prospect for mammalian legged robot when encountering special topographical and unpredictable environment such as obstacles, ditch and so on. This paper surveyed the development process of mammalian legged robots, and mainly introduced overseas and domestic research status in terms of two legged and four legged robots. The related theory and method on legged structure, joint drive, navigation, stability criterion and control algorithm were analyzed and discussed, Meanwhile, the difficulties to be solved under development were analyzed and the future of legged robots was forecasted.


Li J.,Northwestern Polytechnical University | Li J.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.Y.,Northwestern Polytechnical University | Zhang X.Y.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 4 more authors.
Applied Mechanics and Materials | Year: 2013

In quadruped robot, there is the strong correlation of kinematic parameters for the joints of two-section leg, and it is difficult to realize the decoupling of rhythm and pattern over rough terrains. In this paper, we investigated the physiological feature, locomotion characteristics and main function of shoulder blade of quadrupeds, and based on the results, we proposed a stratified control system on the three-section leg to realize better adaptation of a robot to terrains. Through the active control of shoulder blade (frequency and amplitude) and the coupled passive control of upper arm and forearm, a leg may adjust to the terrains of different elevations without changing the movement state of shoulder blade and body speed. In addition, the foot trajectory was planned and a rough terrain was created for testing the athletic ability of a three-section leg, and the validity of the proposed control system is confirmed through simulation. © (2013) Trans Tech Publications, Switzerland.


Zhao W.,Northwestern Polytechnical University | Zhao W.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wang R.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wang X.,Yulin University
2015 IEEE International Conference on Robotics and Biomimetics, IEEE-ROBIO 2015 | Year: 2015

It is well-known that SLIP model is one of the best and simplest abstractions describing the dynamics of hopping and running in animal and human locomotion. Nevertheless, spring-like leg behavior depends on the compliance of limb multiple joints in animal and human locomotion. Therefore, we investigate the influence of biological joint stiffness on running stability based on two-segment leg model. A nonlinear relationship between the virtual leg spring force and the virtual leg spring compression is found because of a nonlinear biological joint torque-angular displacement relationship of elastic two-segment leg. The functional relationship between the virtual leg spring force and the virtual leg spring compression is established, and then based on biological limbs maximum compression in fast running, we establish the equation for solving the radius of cable pulley. At high speed the tolerated minimum dimensionless reference stiffness in two-segment leg model is largely decreased (17 at 29 m s-1, β0=110°) compared with linear leg spring model (45). In fast locomotion, the two-segment leg model with biological joint stiffness can demonstrate outstanding performance for stable running. © 2015 IEEE.


Zhang X.,Northwestern Polytechnical University | Zhang X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Qin X.,Northwestern Polytechnical University | Qin X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 8 more authors.
Jiqiren/Robot | Year: 2013

To address the requirements of high speed and mobility for quadruped robots galloping, a composite rigidflexible structure model is proposed for a single leg of quadruped robots. The composite rigid-flexible structure is designed for a single leg of quadruped robots, and operating characteristics with or without impact loading, stiffness characteristics, D-H kinematics and toe work space are analyzed. After that, taking noise factor such as ground impact under dynamic motion into consideration, linear quadratic Gaussian control is applied to driver control of a single leg of quadruped robots. Then, with vertical hopping as an important basic motion prototype for galloping, analysis and simulation of equal-height jumping control under disabled environment are conducted based on finite state machine and peak height feedback. Finally, continuous vertical hopping experiment of a single leg with composite rigid-flexible structure of quadruped robots is conducted. Analysis and experiment results indicate the rationality of the structure design and the effectiveness of the control scheme.


Liu A.,Northwestern Polytechnical University | Liu A.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Zhang X.Y.,Northwestern Polytechnical University | Zhang X.Y.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

The adaptability of velocity changing of quadruped robot needs to be realized by gait transition. In this paper, a gait transition method of a quadruped robot based on changing the time sequence was investigated. The swing phase and the stance phase are separated by finite-state machine (FSM), and the locomotion gait involves breaking/enforcing synchronization or changing the order of leg liftoff events, it makes the duration time of liftoff and touchdown events variable. The gait transition from walk to trot is realized by the combination driving of time and event. The experiment is verified by interactive co-simulation among Matlab-Adams. The transition method satisfies the velocity changing of quadruped robot. © (2013) Trans Tech Publications, Switzerland.


Liu A.,Northwestern Polytechnical University | Liu A.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Wu H.,Northwestern Polytechnical University | Wu H.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Li Y.,Northwestern Polytechnical University
2013 IEEE International Conference on Robotics and Biomimetics, ROBIO 2013 | Year: 2013

In this paper, a gait transition method of quadruped robot was investigated, which is controlled by changing rhythm. It makes the duration time of liftoff and touchdown events variable through the continuous change of walking parameters, and realizes the gait transition from walk to trot. The quadruped bionic robot is a series parallel-multiple branching of nonlinear inverted pendulum system. The stability of trot gait in gait transition processes to the stability of inverted pendulum, and the balance adjustment is generated basing the original motion. The experiment is verified by interactive co-simulation among Matlab-Adams. The transition method satisfies the continuous and steady movement of quadruped robot in gait transition. © 2013 IEEE.


Zhang X.,Northwestern Polytechnical University | Zhang X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | Qin X.,Northwestern Polytechnical University | Qin X.,Shaanxi Province Digital Special Manufacturing Equipment Engineering Research Center | And 8 more authors.
Jiqiren/Robot | Year: 2013

To address the requirements of high speed and mobility for quadruped robots under unstructured environments, a structure model of hydraulically actuated single leg is proposed. For vertical hopping, a two-phase kinematic model and a three-phase dynamic model of a single leg are established under the structure model. After that, the state analysis on the vertical hopping is conducted, and the inverse kinematics solution and the simulation of the hopping are also implemented for a single leg mass-center's instant vertical hopping with 1.5 m/s. Then, the ground impact on the body structure, the operation characteristics and the output force of the hip joint and knee joint's hydraulic cylinder, as well as the hydraulic system design during vertical hopping are discussed. Meanwhile, taking the periodicity of vertical hopping of a single leg into consideration, a PD (proportional-derivative) iterative learning control algorithm is applied to joint trajectory tracking, based on single leg's dynamic model with hydraulic offset. The simulation results indicate that rapid and robust convergence is achieved in trajectory tracking using the presented model, which offers the design and control references for the succeeding prototype development.

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