## 1 Introduction  
Robots have many increasingly different applications. Recently, their feasibility in various service and industry settings, where interaction with humans or environments is required, has been explored. Among the many possible robot forms for these applications, humanoids can be very effective as they have similar kinematic structures to humans. That is, utilizing two arms and two legs, humanoid robots can perform various tasks in a human-centered environment. In particular, the DARPA Robotics Challenge (DRC) Finals in 2015 demonstrated the potential of humanoid robots for use in disaster-response scenarios [1]. Furthermore, the use of humanoid robots in industrial applications, such as airplane assembly and nuclear power plant cleaning, is now being actively investigated [2].  
As humanoid robots are required to interact with people as well as the environment in industry and service applications, both high performance and safety are important. Thus, several design features should be considered: compliance with unexpected external forces, whole-body motion capability through an increased workspace, and straightforward maintenance.  
Compliance reduces the physical damage or instability from unexpected collisions between the robot and external objects and is an essential design consideration for a humanoid robot. There are two approaches to achieving compliance: hardware methods using low-stiffness actuators and software approaches such as torque-based controllers and impedance controllers [3, 4]. Recently, a method for controlling compliant contact with objects has been proposed through an optimization-based approach [5]. In addition, artificial intelligence-based methods of controlling desired compliance have also been introduced for many applications [6]. However, software methods are limited by their dependence on the performance of a sensory system, with their compliance bandwidth limited by those of the sensors and control systems. Furthermore, if a sensor malfunction or software failure occurs, robot compliance cannot be guaranteed. Therefore, humanoid robots with low-stiffness actuators have recently been developed [7; 8].  
Second, whole-body motion capability is fundamental for various tasks, and a large robot workspace enhances this capability. In the DRC Finals, most teams reported whole-body motion planning as a main factor determining manipulation capability in human-centered environments [9]. For instance, the robot should have the capability to perform complex tasks such as stair climbing, driving, and exiting a vehicle.  
Finally, and most importantly, industrial and service humanoids should be easy to maintain. As humanoid robots frequently interact with humans or objects, they require periodic maintenance to avoid malfunction. Modularization is a dominant approach to easy maintenance and is adopted for many robots [10].  
In this study, the JET humanoid platform shown in Figure 1 is introduced to implement the three features listed above. JET was developed on the basis of THORMANG, which was developed by ROBOTIS and was modified by TEAM SNU for the DRC Finals [11]. Through the new design proposed herein, JET overcomes the THORMANG platform limitations while conserving its advantages. The main aim of the new design is to acquire more practical capabilities suited to industrial and service applications.  
The remainder of this paper is organized as follows. Section 2 describes the THORMANG platform specifications and our design goals, while Section 3 presents the newly developed JET humanoid robot design. Section 4 reports experimental validation of the developed robot and Section 5 concludes the paper.