# Design and Performance of L-CaPaMan2
## 1 Introduction  
Parallel manipulators as a class have been developed as described in [1, 2]. In comparison with serial manipulators, their closed-loop structures are more rigid and precise in positioning, because of the error compensation by others; the ability to reach high velocities and accelerations; and the reduced inertial characteristics for the same load, which can be reached by using lighter actuators. On the other hand, precision is constrained by the smaller workspace, and non-linear behaviour complicates kinematics.  
Two main types of parallel manipulators are widespread: Gough-Stewart platform and Delta robots. The Gough-Stewart structure was developed as a tire-testing machine [3] and is widely used in different types of full flight [4, 5] and drive simulators [6], imitating the movements of airplanes such as Boeing-707, Douglas DC-8, or car, respectively. The Taylor Spatial Frame [7] is an external fixture, based on the same architecture, used in orthopedic medicine for bone recovery or correction. The Hexapod telescope [8] uses the Gough-Stewart structure for positioning. Six actuators scheme is used in space-docking systems, such as the low-impact docking system [9]. The Delta robot has universal joints in its structure, which gives more mobility than the Gough-Stewart platform. However, its larger position workspace can be actively used for efficient industrial pick-and-place operations [10] where orientation control is not required. In RoboCrane [10], a Delta structure has been scaled for weldment operations for ship building. In medicine, it is used for assistance [11] or surgical operations [12].  
Some other structures and schemes with different limb kinematic chains are built for solving field tasks. For example, the Cassino Parallel Manipulator, or CaPaMan, which was introduced in 1997 [13] is a different type of parallel structure. Its mechanics, described in [14, 15], can be used for earthquake simulation [16] and in humanoid robots [17]. In combination with other structures and types, both serial and parallel, it has been used as end-effector in drilling machines [18] and surgical robots [19].  
For all these structures, performance is the key factor, even though it affects the final cost of manufacturing, making high-performance robots expensive and difficult tomanufacture. For study and research needs, daily use, or any other situation where users cannot afford to build an industrial-quality robot, reducing price and manufacturing complexity is critical. Even if educational-oriented robots are generally cheaper, their cost can be significant. For example, the price of DexTAR, a professional educational robot [20], is around 70005. With the development of 3D printing and DIY kits for education robotics, such as Arduino board and its extensions, it has become possible to significantly reduce the price and entry level in robotics. The CaPaMan improvement from [21] is an example of using these technologies.  
The L-CaPaMan, which is presented below, is a prototype for study and research tasks. While keeping the structure of the first prototype [13; 14], new design features, such as rolling-bodies translational joint, are introduced, to increase the overall mechanism performance, which has been evaluated in dynamic simulation. The prototype has been assembled and tested in LARM2; the real system behaviour has been investigated to validate the results of the dynamic simulation.