Cable-Driven Parallel Robots (CDPRs) are a special kind of parallel manipulator that uses cables to control the position and orientation of the mobile platform or end effector. The use of cables instead of rigid links offers some advantages over their conventional rigid counterparts. As cables can only pull but not push, the number of cables (n) required to command the end-effector is always $n+1$. This configuration is known as fully-constrained, and it is the most extended configuration for CDPRs. Although CDPRs have many advantages, such as their ability to cover large working areas, one of their main problems is that their working area (workspace) is limited in comparison to its frame area (planar case) or frame volume (spatial case), due to the minimum and maximum allowed tensions. Depending on these tension values, the workspace can notoriously decrease. In order to tackle this problem, lots of works focus on solving kinematics or dynamics problems for cable sagging, i.e., they take into account sagging when modelling the robot kinematic and include these poses inside the usable robot workspace. Taking into account phenomena such as this increases the mathematical complexity of the problem, and much more complex techniques are required. On the other hand, the lack of workspace problem can be tackled by adding active or passive elements to the robot design. In this sense, this paper proposes two mechanical modifications: to add passive carriages to the robot frame and to use a single cable loop to command the end-effector position and orientation. This work presents the kinematic, static, and dynamic models of the novel design and shows the gain of workspace for a planar case while taking into account different parameters of the robot.

Cable-Driven Parallel Robots (CDPRs) are special manipulators where rigid links are replaced with cables. The use of cables offers several advantages over the conventional rigid manipulators, one of the most interesting being their ability to cover large workspaces since cables are easily winded. However, this workspace coverage has its limitations due to the maximum permissible cable tensions, i.e., tension limitations cause a decrease in the Wrench Feasible Workspace (WFW) of these robots. To solve this issue, a novel design based in the addition of passive carriages to the robot frame of three degrees-of-freedom (3DOF) fully-constrained CDPRs is used. The novelty of the design allows reducing the variation in the cable directions and forces increasing the robot WFW; nevertheless, it presents a low stiffness along the x direction. This paper presents the dynamic model of the novel proposal together with a new dynamic control technique, which rejects the vibrations caused by the stiffness loss while ensuring an accurate trajectory tracking. The simulation results show that the controlled system presents a larger WFW than the conventional scheme of the CDPR, maintaining a good performance in the trajectory tracking of the end-effector. The novel proposal presented here can be applied in multiple planar applications.

Knock remains one of the main limitations for increasing the efficiency in spark-ignition engines. The use of certain alcohol–gasoline blends is an effective way to either mitigate or eliminate knock, allowing the use of higher compression ratios, therefore increasing the efficiency of spark-ignition engines. Methanol and ethanol are alcohols commonly employed for reducing knock, due to their higher octane number and vaporization heat value. Major attention is being paid recently to butanol and its blends with gasoline since they present similar characteristics to gasoline; however, it was found to be the least knock resistant among the three fuels. In the present work, a comparison between the knock performance of methanol–gasoline, ethanol–gasoline and butanol–gasoline blends is carried out, by volume concentrations up to 20 v/v%. This comparison is made in terms of knock intensity and knock probability. Tests are performed in a single-cylinder, variable-compression ratio, Cooperative Fuel Research engine equipped with port fuel injection system, facilitating the comparison against future results obtained by similar experimental facilities. Results obtained allow to reach meaningful conclusions about the capacity of each blend to mitigate knock.

Particulate matter emission from the combustion of fossil fuels is a major concern due to its harmful effects on human health and impact on engine performance. Measurement of the smoke point of these fuels is a key issue in order to assess the tendency of fuels to generate particulate matter. Although certain commercial devices for measuring the smoke point are available, they are very expensive and their precision can still be improved. This paper proposes a novel low-cost device to achieve precise and repetitive smoke point measurements. It is based in an improved image processing algorithm that reduces the measurement error compared to previously developed methods. The device design allows easy adaptation to the smoke point lamp normalized in the American Society for Testing and Materials (ASTM) D1322, without any modification to the lamp.

Cable-Driven Parallel Robots (CDPRs) are a special kind of parallel manipulator which use cables to control the position and orientation of the mobile platform or end-effector. The usage of cables instead of rigid links offer some advantages over their conventional rigid counterparts. As cables can only pull, but not push, the number of cables (n) required to command the end-effector is always n+1. This configuration is known as fully-constrained and it is the most extended configuration for CDPRs. Although CDPRs have many advantages, such as their ability to cover large working areas, one of their main problems is that their working area (workspace) is limited in comparison to its frame area (planar case), or frame volume (spatial case), due to the minimum and maximum allowed tensions. Depending of these tensions values the workspace can be notoriously decreased. In order to tackle this problem, lots of works focus on solving kinematics or dynamics problems for cable sagging, i.e., they take into account sagging when modelling the robot kinematic and include these poses inside the usable robot workspace. Taking into account phenomenons like this increases the mathematical complexity of the problem, and much more complex techniques are required. On the other hand, the lack of workspace problem can be tackled by adding active or passive elements to the robot design. In this sense, this paper proposes two mechanical modifications: to add passive carriages to the robot frame and to use a single cable loop to command the end-effector position and orientation. This work presents the kinematic, static and dynamic models of the novel design and shows the gain of workspace for a planar case while taking into account different parameters of the robot.