# Using a Cable-Driven Parallel Robot with Applications in 3D Concrete Printing
## 2 Mechanical Structure  
### Architecture of the Model  
The structure of a CDPR was researched to find the different configurations for multi-purpose applications [7]; an optimal design of a CDPR usually relate to one which has the largest workspace, the fewest singularities, large force output, high stiffness throughout its workspace, high accuracy, etc. Designing the robot configuration so that it ensures the largest working space, with the constraints of size, flexibility, and load, is the main goal in cable robot designs. The optimized design performance index is a term that describes methods of comparing the optimal design properties of a design configuration compared to other investigated configurations or other robots. A commonly used performance index is the global condition index (GCI) [10], which is a measure of the kinematic dexterity of the robot over the whole workspace. The robot classification is based on the topology of structure into serial and parallel robots. A sequence of joints and links is called serial robots or manipulators and, when there are more than one kinematic chains connecting to the end-effector of platform, it is called a parallel robot or closed kinematic chains. The CDPR is a special type of parallel robot with m being the number of cables and n being the degree of freedom of the CDPR moving platform. We have m \(<\) n + 1 being an under-constrained robot; m = n + 1 is a fully-constrained robot; and m > n + 1 is a redundantly constrained robot [7; 11]. The inverse kinematics of the CDPR are much easier to analyze than the forward kinematics as well as the singularities affecting the robot in a similar way. The structure of a CDPR can be briefly described as follows: m cables are connected the m corners of a moving platform in three-dimensional Cartesian space; when changing the length of cables, the moving platform coordinates also change. We always consider the structure of the CDPR to inhibit the degree of rotation, because the weight of the moving platform plays a role, such as an external force that affects the tension and moves in the vertical axis. The workspace of a robot is an important attribute; it affects how the robot is designed to be suitable for its actual use. The workspace of some types of robots, e.g., a cylindrical robot and gantry robot, can be described with simple geometric primitives such as a cylinder or rectangle. For serial robots, to define the workspace, we can give the basic parameters, such as the length, height, width, radius, kinematic chain, and the limits of the joints. The workspace description gets more complicated when considering translation and orientation or taking into account the dexterity of the robot. For ease of understanding, the workspace model should be simple; however, the topology of the rotation group is not isomorphic to the Cartesian space. Unfortunately, the motion is more complex for parallel robots and especially for cable robots where translation and orientation are strongly coupled. However, since most application engineers have a simple representation of the workspace in mind, one may have to finally reduce the used workspace of a robot to a subset that can be represented by a geometric primitive, such as a box, a cylinder, or a sphere. Cable-driven parallel robots are able to generate high velocities and accelerations due to the very small inertia of their moving parts and cables. Furthermore, a large workspace and high payloads are possible due to efficient force transmission through the cables. A dynamic model extends the kinematic considerations by explicitly taking into account the influence of time on the behavior of the mechanical and also electrical subsystems of the cable robot. The fundamental geometric relations between the fixed base, the mobile platform, and the cables are the foundation of kinematic and static modeling. These nonlinear equations formulate the velocity and acceleration transmission of the robot, and which are employed to characterize the behavior of the robot.