Hi Savitri,
Plan Quality Management is the process where you identify quality standards and requirements, and this may include defining control and specification limits; e.g., whether the usual +/- 3 sigma can be acceptable, or a more restrictive measure should be adopted.
Control Charts - as the graphical representation of the variables you measured to describe a given process - are then used as one of the Control Quality Tools&Techniques to determine whether that process is under control.
Gabriella