A numerically stable algorithm for analytic inverse kinematics of 7-DoF S-R-S manipulators with joint limit avoidance

This paper presents a numerically stable algorithm for analytic inverse kinematics of 7-DoF S-R-S manipulators with joint limit avoidance. The arm angle is used to represent the self-motion manifold within a global arm configuration. The joint limits are analytically mapped to the arm angle space for joint limit avoidance. To profile the relation between the joint angle and arm angle, it is critical to characterize the singular arm angle for each joint. In the-state-of-the art methods, the existence of the singular arm angle is triggered by comparing a discriminant with zero given a threshold. We will show this leads to numerical issues since the threshold is inconsistent among different target poses, leading to incorrect range of the arm angle. These issues are overcome by associating indeterminate joint angles of tangent joints with angles of 0 or pi of cosine joints, rather than using an independent threshold for each joint. The closed-form algorithm in C++ code to perform numerically stable inverse kinematics of 7-DoF S-R-S manipulators with global arm configuration control and joint limit avoidance is also given.

Systems Integration in Infrastructure Projects: Seven Lessons from Crossrail

We propose a systems integration model for the delivery of complex infrastructure projects. We argue that the client is ultimately accountable for systems integration in major projects, setting out the responsibilities to ensure that systems integration is successfully accomplished to achieve desired outcomes. From the Crossrail case, we draw seven lessons for clients, to: 1) manage programme delivery as an integration activity; 2) actively manage systems integration; 3) ensure authority to make decisions; 4) maintain configuration control; 5) plan for a lengthy testing and commissioning phase; 6) appreciate supply chain products may be part of unaligned global R&D and development programmes; and 7) do final integration only when there is something to integrate. Central to our argument is the idea that on such complex projects, the client cannot outsource systems integration and thus needs to recognize they retain accountability, though roles and responsibilities can be assigned to the delivery partner, supply chain, chief engineer and/or contracted systems integration firm. A key question for the client at the outset is how to distribute interface management and systems integration responsibilities while retaining accountability and oversight. Rather than managing through contracts, budgets and schedules, we suggest a changed approach with priority given to managing integration, and contracts, budgets and schedules that support and incentivise this.

Precise semi-analytical inverse kinematic solution for 7-DOF offset manipulator with arm angle optimization

Seven-degree-of-freedom redundant manipulators with link offset have many advantages, including obvious geometric significance and suitability for configuration control. Their configuration is similar to that of the experimental module manipulator (EMM) in the Chinese Space Station Remote Manipulator System. However, finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult. This study proposes a high-precision, semi-analytical inverse method for EMMs. Firstly, the analytical inverse kinematic solution is established based on joint angle parameterization. Secondly, the analytical inverse kinematic solution for a non-offset spherical-roll-spherical (SRS) redundant manipulator is derived based on arm angle parameterization. The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator. Thirdly, the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization. After selecting the stride and termination condition, the precise inverse solution is computed for the EMM based on arm angle parameterization. Lastly, case solutions confirm that this method has high precision, and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.

Peculiarities of Implementation of Configuration Control Processes of Integrated and Innovative Projects of Logistics System Creation

The analysis of the current scientific and methodological principles of project management is performed. It is established that the existing models and methods cannot be used to control the configuration of integrated projects for the creation of logistics systems. The known toolkit provides general approaches to controlling the configuration of projects and does not take into account many factors of the design environment, which determine changes in the configuration of integrated projects for creating logistics systems. It has been substantiated that changes in the configuration of integrated projects for the creation of logistics systems are due to two groups of factors. They can be assessed by four criteria based on the determination of two generalized evaluative characteristics of the influence of the factors of the design environment on changes in the configuration objects of these projects. The scientific and methodological foundations of the configuration control of integrated projects for the creation of logistics systems are proposed, taking into account the changing components of their design environment. To control the configuration of integrated projects for the creation of logistics systems, the use of project management theory and system-factor principles is envisaged, which fully take into account the peculiarities of the implementation of these projects. Based on the proposed model, the impact of internal environment factors of integrated projects for the creation of logistics systems on changes in the configuration object No. 4.1 (a specialized tank truck for transporting perishable goods) was assessed. Significance coefficients are defined for each of the assigned codes (evaluation criteria and factors that determine the configuration changes) of the configuration objects of integrated projects for the creation of logistics systems. Their numerical value is in the range 0…1 and it characterizes the significance of each of the factors for a particular object of the configuration of integrated projects for the creation of logistics systems. Quantitative assessment of the impact of design environment factors on changes in the configuration of integrated projects for the creation of logistics systems is carried out on a 100-point scale.

The spatial configuration control for the mobile digital direction finder system

A promising direction related to determining the location of radio sources is the use of mobile digital direction finders. Their use is most effective when such direction finders form a system of information-related meters localized in a mobile coordinate system and able to move in it. Depending on the variation of the electromagnetic environment (the termination of radiation by some sources, the appearance of other sources of radio emission, their movement, etc.), the positions of the separated digital direction finders inside such a system should change. To ensure the effective functioning of the measuring system, the paper considers the problem of synthesizing control of the spatial configuration of digital direction finders, the solution of which provides maximum accuracy in determining the coordinates of the location of radio sources. It is shown that the specified problem belongs to the class of active experiments optimization problems or problems of trajectory control of observations.