In most projects the project manager is responsible for the workplan and updates it on a weekly or bi-weekly basis. In most projects the project manager is the only one that is allowed to update the plan. However, there are some options, especially for larger projects.
The Project Manager is responsible for clearly defining what is expected from each member of the team.
Project management resources - power goals
Project management resources: Be a project champion
Goal setting helps to create a compelling vision of the project's end result and its value to the organization.
Project team: Finding better ways to reward your team
Project management resources - project team