South Korean researchers have developed a drone designed to stay level when transporting goods over many kinds of surfaces.  韩国研究人员开发了一种无人机，旨在在多种表面上运输货物时保持水平。  A team at Seoul National University of Science and Technology built a prototype, or test model of the drone. The team recently demonstrated the aircraft for reporters from Reuters.  首尔国立科技大学的一个团队构建了无人机的原型或测试模型。该团队最近向路透社记者展示了这架飞机。  The prototype has a transport carrier attached to a drone structure. It is supported by several propellers and rotors that control its height, speed and direction in the air. The aircraft has a handle workers can push to guide it where it needs to go.  该原型机有一个连接到无人机结构的运输载体。它由多个螺旋桨和旋翼支撑，控制其在空中的高度、速度和方向。飞机有一个手柄，工作人员可以推动以引导飞机前往需要的地方。  Members of the development team showed how the drone can keep itself level while floating, even when transporting goods up or down stairs. Leaders of the research say the drone is programmed to predict human actions for effective interactions.  开发团队成员展示了无人机如何在漂浮时保持水平，甚至在上下楼梯运输货物时也是如此。该研究的领导者表示，无人机经过编程可以预测人类的行为，以实现有效的互动。 Lee Seung-jae is a professor of mechanical system design engineering at Seoul National University of Science and Technology. He was a leader of the project. The research results appeared in a study in IEEE Robotics and Automation Letters. The publication is part of the Institute of Electrical and Electronics Engineers, based in New York.  Lee Seung-jae 是首尔国立科技大学机械系统设计工程教授。他是该项目的领导者。研究结果发表在《IEEE 机器人与自动化快报》的一项研究中。该出版物是纽约电气和电子工程师协会的一部分。  Lee told Reuters tests of the drone showed it could transport objects up to 3 kilograms. He admitted this weight restriction likely limits the drone’s use cases for many businesses. But he noted that the transporter’s design and operating equipment could be used to create a series of other kinds of drone vehicles.  Lee 告诉路透社，无人机的测试表明它可以运输重达 3 公斤的物体。他承认这种重量限制可能会限制无人机在许多企业中的使用案例。但他指出，运输机的设计和操作设备可用于制造一系列其他类型的无人机。  Lee said one example would be to use the transporter to carry sensitive or breakable materials. The technology could also be used to develop “flying taxis” to transport humans, he added.  李说，一个例子是使用运输车运输敏感或易碎材料。他补充说，该技术还可用于开发“飞行出租车”来运送人类。 When used in a flying taxi, Lee said the drones could be used to change batteries while still flying in the air, instead of having to return to a ground station for recharging.  李说，当用于飞行出租车时，无人机可以在空中飞行时更换电池，而不必返回地面站充电。  In general, experts say drones with multiple propellers are easier to control and move in many different settings. But they are also slower and cannot travel as far on a battery charge.  一般来说，专家表示，具有多个螺旋桨的无人机在许多不同的环境中更容易控制和移动。但它们的速度也较慢，并且无法通过电池充电行驶那么远的距离。  Drones with multiple rotors have already been used to transport small amounts of goods, food and medical supplies. But experts say it is difficult to widely expand use of such drones for commercial purposes. This is because such activit