Writing instrument

A writing instrument comprising:

• a proximal end configured to contact a writing surface, and a distal end, wherein an attachment for the writing instrument is removably attached to, or integrally formed with, the writing instrument;
• the attachment comprising:
• a support member, wherein the support member comprises a distal end (D) and a proximal end (P), wherein an attachment axis (A) is defined between the distal end and the proximal end, wherein the support member is configured to be attached to the writing instrument, wherein
• an inertial measurement unit, wherein the inertial measurement unit is configured to measure a movement of the attachment axis (A) between a first and a second position of the attachment axis (A);
• a momentum wheel assembly, wherein the momentum wheel assembly comprises a first rotatable member coupled to a first motor, wherein the first motor is configured to apply a variable torque to the first rotatable member, wherein the momentum wheel assembly further comprises a second rotatable member coupled to a second motor, and a third rotatable member coupled to a third motor, and wherein the second and third motors are configured to apply variable torques to corresponding second and third rotatable members;
• and
• a control unit configured to actuate the first motor based on the movement of the attachment axis (A) measured by the inertial measurement unit.

A method for assisted writing, comprising:

• detecting, during a writing operation, one or more movements of a position of an attachment axis (A) of an attachment, when the attachment is attached to a writing instrument;
• generating one or more movement signals characterising the one or more movements;
• generating at least one correction torque to be applied to the attachment by at least a first rotatable disk based on the detected one or more one or more movement signals of the attachment axis (A);
• actuating at least a first motor of the attachment to apply the correction torque to the first rotatable disk;
• using the one or more movement signals to identify an attempt to form a predefined symbol by comparing the one or more movement signals to (i) a model, or (ii) a control loop, or (iii) a database of motion characteristics;
• and
• predicting a subsequent symbol to be formed, based on the attempt to form the predefined symbol, wherein the correction torque is dependent on the subsequent symbol.