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IEEE Spectrum:Bipedal Robot Uses Jet-Powered Feet to Step Over Large Gaps

字体: 2018年03月23日 浏览量: 作者:Evan Akerman 编辑:朱小翠 来源:IEEE Spectrum 2018/03/20

 

国际著名杂志IEEE Spectrum官网自动化专栏

就仿人机器人研究专题采访广东工业大学黄之峰副教授

 

利用喷射推力越障的双足机器人

利用安装在机器人脚掌前端的涵道风机产生的推力实现双足机器人大跨步时的姿态平衡

(作者:Evan Ackerman

照片来源:广东工业大学

安装在Jet-HR1脚掌的涵道风机能使机器人比普通机器人跨得更远而且不摔倒

 

你可能已经注意到,双足机器人在跨步过程中有一种倾倒的趋势。因为这涉及到移动时要在一只脚上保持平衡。所有的步态并不是一成不变的,当然,你可能很容易在平整的地面跨出一步,但是当你试图通过跨越的方式来避免与障碍物碰撞时,这一步将变得难以跨出。机器人和人类的步态都受限于其在不倾倒的前提下所能跨出的步距。人类通过动态行走在一定程度上减少了这种限制,但同样也会一直往前倾。而对于需要执行准静态动作的机器人来说,可跨越步长极大的限制了它们所能跨越的障碍物。

根本的问题在于你越想跨越得远,质心也会更加偏向你跨越的方向。尝试着跨一大步,在你伸腿时你会往前倾。(请不要轻易去尝试这个动作)

对准静态条件下的机器人(或人类)来说可以通过改变质心来解决,也可通过减轻伸出腿的质量,或者增加其他部分的重力解决。而在中国广东工业大学自动化学院的一个实验室,实验人员用固定在双足机器人脚掌的小型涵道风机来进行实验。这个方案成功使得双足机器人能够调整自身重心维持平衡,跨越过一条正常情况下无法跨越的宽沟时。

图片:相片:广东工业大学

涵道助推系统安装原理图

 

这个机器人叫Jet-HR1(JetHumanoidversion1喷射仿人机器人1号),重6.5kg,高650mm, 在每只脚脚掌前端装有涵道风机引擎,涵道风机重量232g,但是输出的推力可达2kg,将近机器人总重量的三分之一。

在一实验中,Jet-HR1执行跨越370mm宽沟渠的任务,这到达了其腿长的80%。为了完成这个任务,机器人伸出腿的同时开启涵道风机,不可或缺的向上托着跨越的腿以防止机器人向前倾倒。一旦装有涵道风机的跨越腿到达了沟渠的另一侧。机器人的后腿也重复这一过程,完成跨越。整个跨越过程可以顺畅地在一分钟内完成,这速度十分迅速。

研究者建议说这种一般性的技术能适用于其他许多具有挑战性的情况,当机器人遇到它需要跨越的大尺度障碍物时,能够帮助其实现平衡控制,或者在一般不平整地面保持平衡不摔倒。因为涵道引擎能够保证在于地面不发生接触的情况下动态调整机器人的质心,你可以设想各种脑洞大开的事,例如机器人在复杂环境中侧向倾斜行走。

为了更加了解Jet-HR1,我们通过邮件,对广东工业大学的黄之峰副教授进行了采访。(以下为采访内容):

IEEE Spectrum: 你是怎么想到把涵道风机像图中那样放在脚掌上的?

黄之峰:我们或多或少的受到科幻小说的启发。但实际上,我们两年前就开始考虑这个方案了,那时,我们注意到地震废墟中的糟糕地形,给仿人机器人的移动带来很大限制。双足机器人跨越大尺度障碍物是困难的,因为跨得太远会打破静态平衡条件,这个条件需要机器人质心在地面的投影位于其脚底的支撑多边形之内。而另一些动态动作,例如跳跃,也可以考虑为一种解决方案,但是其着地的冲击会可能会造成本来就不坚固的地面发生二次坍塌。

这就是我们需要一种新的方法来保持机器人的准静态平衡的原因。利用涵道风机构成的推进系统不仅可以保持机器人的平衡,还能够有效降低机器人落脚时产生的冲击

IEEE Spectrum:涵道风机能让机器人的性能有多大的改善?

黄之峰:目前,在准静态条件下,涵道风机主要是改善机器人在不同姿势下保持平衡的能力。利用涵道风机的推力,机器人的可跨越距离可以得到有效提高。正如视频中的实验所示,即使没有上半身对重心进行调整,双足机器人也能够完全跨过450mm宽的沟,这个宽度达到了其腿长的97%。在先前的其他仿人机器人研究中,这个数据一般只有20%。

IEEE Spectrum:还有什么其他的步态或动作能从涵道助推系统的帮助中受益?

黄之峰:涵道助推辅助不仅有利于2D步态,同样也有利于3D步态和动态动作,如跳跃。此外,涵道推进系统用使得一些特殊的3D步态成为可能。例如,机器人可以借助涵道风机的推力实现在单脚支撑的情况下原地甩动另一条腿(以获得旋转力矩)。此外,涵道风机也有助于减小动态动作的冲击。

IEEE Spectrum:你认为这样的系统对仿人机器人越障来说是一个实际可行的方案吗?

Jet-HR1由一对装有电动涵道风机的机器腿组成,对于更大的机器人,研究者建议更加强劲的涡喷引擎以满足要求。

 

黄之峰:是的,从目前结果看,这个解决方案是完全可行的。对于质量小于

15kg的机器人,助推系统可以由电动涵道风机组成,而对于对于质量大于15kg的仿人机器人,可以考虑涡喷引擎。这两种推进器都是成熟的技术,尤其是电动涵道风机。

IEEE Spectrum:如何改善这个系统?接下来主要研究什么?

我们正解决这个系统的实际应用中所面临的问题。当前,实验室的一个小组正在解决电源问题(例如高能量密度电池)和推力精确反馈馈控制。另一个小组则主要负责机器人运动规划和控制器。未来的研究重点将放在动态跨越和软着陆技术。这将使机器人以更快更少冲击的跨越障碍物。此外,在涵道推进系统辅助下的一些全新的3D步态也在不断地进行尝试。

“Jet-HR1: Two-dimensional Bipedal Robot Step Over Large Obstacle Based on a Ducted-fanPropulsion System,”作者是来自广东工业大学的黄之峰,刘彪,魏嘉鹏,林清生,章云,以及太田顺和(东京大学)。该论文已发表在2017仿人机器人国际学术会议上。并且我们期待在IROS 2018见到最新的进展。

 

 

 As you may have noticed,. This often happens when the robots are trying to take a step,because stepping involves balancing on one foot while moving. All steps aren’t equal, of course—you’ve got easy steps, when you’re walking slowly across a flat surface, and you’ve got hard steps, when you’re trying to avoid an obstacle by stepping over it or across it. Both robots and humans are constrained in the kinds of steps we’re able to take by (among other things) how far we can stick a leg out without falling over. Humans mitigate this to some extent by dynamic walking, also known as constantly falling forward, but for less dynamic (quasi-static) robots, step length puts a significant limitation on the kinds of obstacles they can deal with.

 

The fundamental problem here is that the longer the step you want to take, the more your center of gravity moves out toward the leg you’re taking the step with. Try to take too big of a step, and you’ll fall forwards while extending your leg. Go on, try it!*

 

Solving this for a quasi-static robot (or human) can be done by changing the center of gravity somehow, either by reducing the weight of the leg you’re sticking out, or increasing the weight of all of the rest of you. At Guangdong University of Technology’s in China roboticists are experimenting with using small ducted fans embedded in the feet of a bipedal robot. The idea is to change the robot’s center of gravity to help it balance as it takes giant steps over a wide gap that it normally wouldn’t be able to cross.

           

Photo: Guangdong University of Technology

The ducted fans on Jet-HR1's feet allow the robot to stretch its legs out

farther without falling and take bigger steps than it normally would be able to.

 

The robot, called Jet-HR1, weighs 6.5 kilograms and has a height of 65 centimeters. On the end of each foot is a ducted fan jet engine, which weighs just 232 grams but can output up to 2 kg of thrust, nearly a third of the weight of the entire robot.

 

In one experiment, Jet-HR1 was tasked with stepping over a gaping chasm 37 cm wide, which required a step length of 80 percent of its leg. To make this work, the robot spooled up the ducted fan as it stuck its leg out, essentially holding the leg up and preventing the robot from tipping forwards. Once the robot has its jet foot planted on the far side of the gap, it repeats the procedure with its back leg to complete the crossing. The entire maneuver can be completed in well under a minute, which is pretty quick, as is appropriate for a robot with two jet engines on it.

 

The researchers suggest that this general technique could be adapted to many more challenging situations, by helping robots control their balance when facing large obstacles that they need to step over, or even just keeping them from falling over when managing roughterrain in general. Since the jet engines allow the robotto dynamically adjust its center of mass without the need for specific ground contacts, you can imagine all kinds of crazy things

(/automaton/robotics/humanoids/jet-powered-icubcould-be-the-first-flying-humanoid-robot)like robots that tilt themselves sideways or even do the limbo to  navigate complex environments.

For more about Jet-HR1, we spoke with Zhifeng Huang, an associate professor at Guangdong University of Technology, via email.

 

 

IEEE Spectrum:How did you get the idea to put jets on the feet of a robot like this?

 

 

ZhifengHuanWe were more or less inspired by science fiction. In fact, we considered this idea two years ago, when we noticed the mobility limitation of humanoid robots when going through rubble and debris in an earthquake aftermath scenario (e.g. the DARPA Robotics Challenge).

(/automaton/robotics/humanoids/darpar-robotics-challenge-monents-lessons-learned-whats-next).It’s difficult for a bipedal robot to step over large obstacles, since extending the legs too much would disrupt the static balance condition, which  requires the robot’s center of mass to be projected inside the support area of its foot. Some dynamic motions, such as jumping, might be considered as a solution. However, this might not be suitable for irregular terrain, as the impact of the robot when it lands might cause it to fall over.

That’s why we think a new method that enables the robot to maintain a quasi-static balance and produces a less significant impact while it steps over obstacles is necessary. And our idea was utilizing the external force of the jets to maintain the balance of the robot.

 

 Image: Photo: Guangdong University of Technology

Schematic of the ducted-fan propulsion system mounted

on each foot.

 

How much of a difference did the jets make to the performance of the robot?

 

 

Currently, in the quasi-static condition, the jets mainly improve the robot’s ability to keep its balance under various postures. Using the thrust of the jet, the distance that the robot’s foot can be placed extends. As hown in the demo video, even without an upper body, the robot was able to completely step over a broad gap with 45 cm in width, up to 97 percent of its leg’s length. In previous studies, only around 20 percent was possible.

 

What other kinds of gaits or maneuvers could benefit from jet propulsion assistance?

 

 

The jet propulsion assistance could benefit not only 2D gaits but also 3D gaits and some dynamic motions, such as jumping. It could also make some special 3D gaits possible. For example, with just thrust, the robot might be able to rotate its body while one foot is supporting itself and the other leg is swinging. In addition, the jets are helpful in reducing impacts whileperforming dynamic motion.

 

Do you think that a system like this could be apractical way for humanoid robots to move over obstacles?

 

Yes, current results show that the solution is entirely feasible. For a robot whose weight was lower than 15 kg, the propulsion system consists of electric ducted fans. For a humanoid robot whose weight is larger than 15 kg, turbojets might be considered. Both are mature technologies.

 

How could this system be improved? What are you working on next?

 

We are working on some practical applications of this system. Currently, one team in my laboratory has been working on the power source (e.g. high density battery) and the precision feedback control of the thrust. Another team is focusing on the robot’s locomotion planning and controller. Future studies will focus on dynamic stepping and soft-landing techniques, which may enable a robot to step over obstacles more quickly and with less impact. In addition, some new 3D gaits with the help of the jets will also be explored.

 

“Jet-HR1: Two-dimensional Bipedal Robot Step Over Large Obstacle Based on a Ducted-fan Propulsion System,” by Zhifeng Huang, Biao Liu, Jiapeng Wei, Qingsheng Lin, Jun Ota, and Yun Zhang from Guangdong University of Technology in China, was presented

 

 

Jet-HR1 consists of a pair of robot legs with electric

ducted fans on its feet. For larger robots, the

researchers say more powerful turbojets might be

required.

 

 

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